To explore the effects of physical activity on anxiety levels in college students, as well as to examine the mediating role of emotion regulation. A convenience sample of 1,721 college students from Shanghai, Jiangsu, Shandong, Guangxi, and Hunan was used to conduct an evaluation and a survey through the Physical Activity Rating Scale (PARS-3), the Anxiety Self-Rating Scale (SAS), and the Emotion Regulation Scale (ERQ). College students' anxiety level, cognitive reappraisal, and expression inhibition scores were (44.72±10.37), (30.16±6.51), and (16.96±4.99), respectively. There were significant grade and physical activity level differences in anxiety levels and cognitive reappraisal, and significant gender and physical activity level differences in expression inhibition among college students. Process model 4 mediated effect regression analysis showed that physical activity had a significant positive effect on cognitive reappraisal (R 2 = 0.14, β = 0.04, P<0.001), and physical activity did not have a significant expression inhibition effect (R 2 = 0.17, β = 0.01, P = 0.27). Physical activity (β = -0.03, P = 0.012), cognitive reappraisal (β = -0.59, P<0.001), and expression inhibition had a significant effect on (β = 0.57, P<0.001) anxiety levels (R 2 = 0.37). In the model effect relationship, the direct and indirect effects of physical activity on anxiety levels were -0.028 and -0.019, respectively. Physical activity has a significant negative effect on college students' anxiety levels. Cognitive reappraisal is a mediating variable for the effect of physical activity on anxiety levels. The higher the level of physical activity and the higher the intensity of the activity, the lower the level of anxiety.