In Half a Loaf of Kung Fu, the protagonist, played by Jackie Chan, is a young man who fantasizes about becoming a martial arts hero. One day, he discovers a book belonging to a famous martial arts master who recently passed away. The book contains the secret techniques of the master's kung fu style, which the protagonist studies and practices.
To impress a girl he likes, the protagonist claims to be the deceased master and gains the attention of various martial arts clans who seek to obtain the master's artifacts that are being transported by an escort company. These artifacts are said to contain the key to a powerful kung fu technique that could make one invincible.
The protagonist soon finds himself caught up in a dangerous game of cat and mouse as he tries to outwit the different clans and protect the artifacts. Along the way, he enlists the help of a bumbling kung fu master who becomes his reluctant sidekick.
The movie features several humorous fight scenes and stunts typical of Jackie Chan films, showcasing his signature blend of physical comedy and martial arts action. In the end, the protagonist must face the final showdown against the most powerful clan leader to save the artifacts and prove his worth as a true martial arts hero.