Seventeen-year-old Mulan is one of the most beautiful and talented women in Hebei. The fact that she is engaged to marry Wang Qingyun, one of the few young men who managed to exempt himself from the previous drafts, makes her the envy of the entire village. However, when Mulan’s father (a retired battalion captain by the name of Hua Hu) is called to serve in the army, her world turns upside-down. Because her siblings are still very young (her Munan nine years old while her brother Yaoer is five), Mulan volunteers to takes her father’s place in battle. Dressing as a man, she gives up everything she has ever know to join the army.
The men are sent to Black Mountain to eradicate bandits who have taken control over mountain passes which are critical to trade routes. Due to racial tensions, Supreme Commander Xin Ping decides to divide the newly formed army into two companies. As he reads through the credentials of the men who have been conscripted, he notices that almost all of the seasoned warriors are Xianbei; the only man among the Chinese soldiers who has fighting experience is Hua Hu. When Xin Ping calls Hua Hu’s name, Mulan steps forward. After she demonstrates her military prowess, Mulan is promoted to captain over the Chinse men.
The leader over the Xianbei men, as well as vanguard over the entire expedition, is a man by the name of Niu He. The Xianbei camp is attacked in the middle of the night and Niu He flees for his life, but Mulan quickly leaves her camp behind to rescue the Xianbei men from disaster. As the bandits flee, Mulan orders the men forward in pursuit and captures several bandits. When Niu He returns, he is embarrassed. In order to conceal his failures, he refuses to reward Mulan for her service but reports that the victories were his own.
Because no further victories are won, Xin Ping comes to investigate why the army is having such difficulty eradicating the bandits. Upon sensing Niu He’s incompetence, Xin Ping decides to personally take leadership over the expedition. Xin Ping orders that one of the bandits (whom Mulan had captured) be released from prison. Xin Ping interrogates the bandit and discovers a weakness in the enemy’s stronghold. As a result, he manages to capture Heaven Cather, one of the three bandit ringleaders.
Earth Master comes to rescue Heaven Catcher and is about to kill Niu He, but Mulan dashes onto the scene. Earth Master is badly defeated and the bandits retreat. Out of fear, they retreat into an impenerable fortress. Xin Ping and his men spend the next six years laying siege to the bandit’s stronghold.
The emperor grows impatient and orders the army to advance at any cost, threatening to execute the officers if they continue being idle. During an emergency meeting, Niu He steps forward and suggests sending Muan with a letter offering amnesty if the bandits surrender. He does not expect this plan to work; rather, he simply wants to eliminate Mulan out of jealousy. Because nobody has any better ideas, Mulan agrees to go on this suicide mission.
Earth Master recognizes Mulan as the soldier who defeated him and desires revenge but remembers that if he kills Mulan, the life of his brother Heaven Catcher will be at risk. His adviser proposes a way to trap Mulan inside the bandits’ stronghold without using force. Mulan (whom they think is a man) is presented with a choice between death and marrying Princess Lu Wanhua. Mulan reluctantly consents to go forward with the wedding.
When Mulan refuses to consummate the wedding, Princess Wanhua grows suspicious and eventually discovers that Mulan is a woman. Finally, Mulan shares her story, and Wanhua is so impressed that the two women become sworn sisters. Wanhua agrees to betray the bandits and work to destroy them from within.
Before she departs, Mulan confides her insecurities in Princess Wanhua. When she first left, she had not intended to be away for this long. Being that almost all the young men have been drafted, her fiancé has been living in a town of women for nearly seven years. Mulan has little doubt that Qingyun has already married, and is uncertain whether these years that she has spent living among men have lowered her value beyond even hoping to become his second wife. Finally, Princess Wanhua comes up with a solution which both of them feel will convince Qingyun to marry Mulan: If he will take Mulan in marriage, Wanhua will agree to serve as his mistress. Mulan feels relieved and is eternally grateful to the princess.
In order to escape, Mulan dresses as a woman. However, the bandits have anticipated this. The guards are ordered not to let any men out, and women who exit must prove their feminity by wearing lotus shoes. When Mulan still manages to return to her camp undetected, the bandits conclude that she must be a master of dark magic.
Mulan gets lost on the way back and ends up on the wrong side of the mountain. Right before nightfall, she suddenly realizes that she is hopelessly lost. Suddenly, Li Jing (mentor to Mulan’s grandfather in Biography of Extraordinary Mulan) appears and gives her a magical bow and arrow. Then, Li Jing transports Mulan back to her camp through the use of magic.
Meanwhile, Princess Wanhua convinces the bandits to feign surrender. They invite Supreme Commander Xin Ping and his army into their stronghold, hoping to capture them. Although Xin Ping knows this is a trap, he recalls the emperor’s orders to advance at any cost. Meanwhile, the bandits are prepared. Three thousand bandits are ordered to fight only against Mulan, whom they believe to be a wizard. During the battle, Mulan is seriously injured and is about to die, but Princes Wanhua drags her to safety. During the chaos, Princess Wanhua sneaks behind the bandit leaders kills them and then flees to “assist” Leopard Skin, the mighty bandit king.
The army advances to confront their final opponent, Leopard Skin. Mulan, who has three broken ribs, is forced to remain behind. For the next three months, Mulan is in critical condition and fades in and out of consciousness. When she finally recovers, she is surprised to find that the doctor shows no signs of having discovered her identity as a woman while restoring her ribs. This remains a mystery which will be not be solved until much later.
When Mulan is finally strong enough to fight, she rejoins the army and finds that they have been locked in a battle against a sorceress, Huang Fengshan, for the past three months. The sorceress has killed many of the army’s mighty men, including Vanguard Niu He. Mulan boldly marches onto the battlefield to confront the sorceress and defeats her with the magical bow and arrow which she had received from Li Jing. Upon seeing that their hero has been defeated, Leopard Skin and the bandits flee back to their heavily fortified stronghold and refuse to come out. Xin Ping and his men spend the next year laying siege to the bandit’s fortress.
Meanwhile, the emperor has lost his patience with the expedition against the bandits. This operation, which was originally supposed to last a few months, has now lasted for over seven years. He orders that an examination be conducted to find the most brilliant man in all of China. Wang Qingyun, Mulan’s fiancé, is chosen and is sent to supervise the army. When Mulan hears that Qingyun is coming, she becomes bashful and refuses to allow him to see her dressed as a man because she wants him to remember her only as a beautiful woman.
Qingyun investigates the bandits’ stronghold and concludes that the only way to force them out is to create an avalanche. He sends a memorial to the emperor, requesting that ten barbarian cannons be constructed and sent up the mountain. After the cannons arrive, Qingyun uses them to induce an artificial landslide. Mulan captures Leopard Skin and Princess Wanhua forces the bandits to surrender.
Mulan returns home and is shocked to realize that Qingyun is still unmarried. For the past twelve years, he has waited faithfully for her. The two of them are married and Mulan gives birth to two children—a boy and a girl.