Dou Yin, known as TikTok, was launched in China in September 2016.This app allows users to create or view 15 to 60-second videos, soundtracked by music clips.After several years it was launched in the market, the downloads gradually surpassed the downloads of FaceBook.In this paper, the author analyzes why DouYin is so popular that it is able to attract such amounts of people.The author separates users into three groups according to their ages: adolescents (14 to 25 years old), middle-aged people (25 to 50 years old), and the elders (older than 50 years old).By analyzing what kind of videos they have a crush on watching and what type of bloggers they love to pay attention to,the author is capable of gaining a piece of comprehensive and holistic information,preferences, and hobbies of the customer.The researcher finds that DouYin provides services that could meet needs of people of different ages.For the adolescents, DouYin provides them with videos that they are interested in a lot and the chance to shopping by spending less time and energy.For the middle-aged people, DouYin needs their needs by offers them opportunities to relax and to be sociable.For the old men and women, DouYin makes them able to pass time and learning new things.Thanks to the overall and holistic functions given by DouYin, it gradually becomes one of the most popular short-time video applications.