Commentary is an applied style to explain, explain and introduce people, pictures, exhibits or tourist landscapes. It takes the form of oral or written explanation, or introduces people's experience, identity, contribution (achievement) and social evaluation, or explains the nature, characteristics, forms, causes, relationships and functions of things. It has two functions: first, it complements the vision, so that the audience can get the description and explanation of the image from the hearing while watching the objects and images, thus being infected and educated; The second is to play a supplementary role in hearing, that is, to let the audience feel the environment in the story immersive, so as to achieve emotional resonance. The average corporate promotional film is 5 words a second. Five minutes is 1500 words. The opening, ending, special effects packaging and transition of the promo all take some time, which takes 30 seconds to one minute, so the number of words is about 1200 words-1300 words.