Abstract: Based on the data of the 2019 population sample survey and the 2016 survey of children and adolescents' physical activities, the population prediction method is used to predict the scale, structure and development trend of Chinese children and adolescents who regularly participated in physical exercises. The results show that from 2020 to 2050, the population size of children and adolescents regularly for physical exercises will increase first and then decrease and finally gradually stabilize. It is estimated that by 2050, the number of children and adolescents who regularly take part in physical exercise will be about 168 million, 139 million and 121 million according to the three population prediction schemes of high, medium and low total fertility rates. The demands for junior sports events, activity organization, participation events, sport venues and fitness guidance will also change with the change of scale, showing a general trend of small increase in the short term and continuous decrease in the medium and long term. To deepen the implementation of the integration of sport and education, more attention should be paid to the changing trend of the population of children and adolescents in China and the new trends, needs and problems of the change in children and adolescents' physical activities under the new situation should be grasped when formulating the 14th Five-Year Development Plan of China's youth sports and the Long-Range Objectives Through the Year 2035.