Take the Chinese food documentary A Bite of China as the example, it plays an important role in the creation of the film. It is an important aspect of the documentary to convey authenticity and express emotion, to tell the story and to control the rhythm. In each episode of 8-9 stories, the director will give the film crew the prescribed actions, including the fact that each story is to be photographed in a dialect map, that is, some typical local sentences spoken by the protagonist of the story, with strong local characteristics. The locals will listen to their hearts and minds, and outsiders will know where this is. In addition, if the protagonist is talented, he will record his song. The hero’s voice can convey an emotion in addition to national characteristics and regional characteristics. In addition, due to the limitations of the radio equipment, it is impossible to pick up the voices of all the speakers in the group communication. Therefore, it is necessary to know the most active and most likely sparking characters in the early stage, and set a microphone for these characters to perform special recording. It is possible to capture a wonderful conversation moment, and the Chinese director on the Bite of China will choose to use different soundtracks according to the rhythm of the picture to reflect the theme. In the fast-cut lens, the director uses relatively light music; while in the detailed picture, it uses relatively gentle music; when showing the growth of everything, the completion of food fermentation, etc., generally adopts more powerful music; In the scenes of the hard work of the working people, more music with more rhythm is used as the soundtrack.