<p>This study investigates how physical activity (PA) impacts subjective well-being (SWB) in college students, focusing on the novel mediating role of rumination and the moderating effects of the Behavioral Activation System (BAS) and the Behavioral Inhibition System (BIS). A cross-sectional survey design was employed, with 1,079 college students participating. Using the SPSS PROCESS macro, the study analyzed the mediating effect of rumination and the moderating role of BAS and BIS. Results showed that: (1) PA significantly predicted SWB; (2) rumination partially mediated the relationship between PA and SWB, with increased PA reducing rumination and enhancing SWB; (3) BAS strengthened the negative predictive effect of PA on rumination and weakened the negative impact of rumination on SWB; (4) BIS weakened the negative predictive effect of PA on rumination and amplified the negative impact of rumination on SWB. This study provides new insights into the role of cognitive processes and individual differences in emotional regulation systems in shaping well-being. These findings contribute to strengthening existing theoretical frameworks and offer practical implications for developing targeted psychological interventions to promote mental health.</p><p> <?noindent??><b>Clinical trial number</b>: Not applicable.</p>