Abstract: An increasing number of studies have been confirmed for the beneficial effects of physical activity on cognitive ability.This paper firstly illustrates the impact of physical activity on cognitive ability from the observational study of cross-sectional and longitudinal, and then summarizes the characteristics of physical activity effect on cognitive ability from randomized controlled trials, explores possible mechanisms for the physical activity effect on cognitive ability from the human body to the animal experiments.Especially in recent years, along with the development of epigenetics research provides a new theory and perspective to explore the molecular mechanism.Finally, the author summarizes the study results consistent with the existing researches, refines its practical guiding significance in the life, analyzes their defects and breakthrough point, and hopes to provide some ideas for the future research.