Appropriate animation rhythm, including internal and external one, can provide audience with unique aesthetic feeling. The internal rhythm contains three forms of expression: describing the details, fluctuating the story and rendering the music. The external rhythm covers many forms, such as pause and montage of the picture, variation of the light and color. Only with harmonious combination of internal and external rhythm the entire perfect rhythm can be designed and cartoon works can be created catering to the audience in order to promote the rapid development of animation industry in China.