<p>Childhood trauma and prosocial behavior have received increasing attention in research on college students, yet the psychological processes linking these variables remain insufficiently integrated. This investigation looked at whether the connection between childhood trauma and prosocial behavior among college students was mediated by self-compassion and cognitive reappraisal, and whether it varied across levels of physical activity. Using standardized measures, data were collected from 1200 college students in China. After controlling for grade level, left-behind experience, and single-parent household background, the data were analyzed using the PROCESS macro. The outcomes demonstrated that childhood trauma was significantly and negatively related to prosocial behavior. Self-compassion and cognitive reappraisal each showed significant mediating effects, and they also formed a significant chain mediating pathway. Of the entire effect, 42.63% came from the indirect effect. Further comparisons indicated that the two distinct indirect impacts through self-compassion and cognitive reappraisal were comparable in magnitude, and both were significantly stronger than the chain indirect effect. Physical activity did not regulate the relationship between childhood trauma and self-compassion, but it showed a modest but significant moderating effect on the relationship between childhood trauma and prosocial behavior so that at larger doses of physical activity, the negative correlation was less pronounced. These findings extend understanding of how childhood trauma is linked to prosocial behavior in college students by highlighting the roles of self-related processes, cognitive-emotional regulation, and behavioral conditions.</p>