<p>The purpose of this study was to investigate the impact of perceived social adversity on prosocial behavior among college students, with a focus on the mediating role of belief in a just world and the moderating role of expression suppression. Study 1 employed a questionnaire survey to explore the relationships among perceived social adversity, prosocial behavior, and belief in a just world. Study 2 utilized an experimental design to manipulate perceived social adversity, further verifying its effect on prosocial behavior and the mediating role of belief in a just world. Study 3 manipulated different levels of expression suppression to examine its moderating effect in the process by which perceived social adversity influences prosocial behavior through belief in a just world. The results showed that perceived social adversity inhibited individuals’ prosocial behavior; belief in a just world mediated the relationship between perceived social adversity and prosocial behavior; and expression suppression significantly moderated the relationship between perceived social adversity and prosocial behavior. These findings reveal the influence of perceived social adversity on prosocial behavior and its underlying psychological mechanisms, providing a theoretical foundation for the maintenance of social order and the development of individual moral behavior.</p>