Abstract In recent decades, there is a decreasing trend in physical activity, which might be associated with decline in physical and mental health among children and adolescents in China. The outbreak and spread of the COVID-19 further aggravated this trend. Under the background of normalized epidemic prevention and control, in order to deeply understand the relationship between physical activity and physical and mental health of children and adolescents, this study sorted out relevant domestic and foreign literatures, and analyzed the effects of physical activity on children and adolescents health and fitness. The positive effects of physical activity, cognition, and mental health were found to be significantly different in the type, intensity, and time of physical activity in the related health effects.