The words “Li” and “Lixue” exist for a long time in Chinese. The meaning of “Li” is initially a direct and intuitive description of “human force”. Later, it developed for the description of the gravity of general objects, and then to the description of the causes of motion state change. This paper analyzes the changes of the meaning of “Li”. Chinese “Lixue (mechanics)” comes as the result of the introduction of Western learning to the East, and there are many twists and turns in the process of determining the subject name. This paper analyzes the process of determining “Lixue” as the subject name, and reveals the change of ancient Chinese understanding of “Mechanics”.