<p>Given how quickly information technology is developing and how diverse online worlds are becoming, research on the cyber behavior and psychological mechanisms of university students has become an important topic in educational and cyber psychology. Unlike previous studies, this research innovatively integrates normative beliefs about aggression and perceived online anonymity into a unified analytical framework, and introduces moral disengagement as a key mediating variable to explain the underlying psychological mechanism. Grounded in the General Aggression Model and Social Cognitive Theory, this cross-sectional study collected questionnaire data from 738 university students to thoroughly examine the relationships among these variables. The results indicate that normative beliefs about aggression and perceived online anonymity are positively associated with cyber aggression, and moral disengagement exerts a partial mediating effect. This study extends our understanding of cyber aggression through an empirical focus on the distinctive features present among university students, investigating the dual pathways of normative beliefs about aggression and perceived online anonymity, and systematically revealing the key mediating mechanism of moral disengagement. These results offer a fresh theoretical framework for comprehending how cyber aggression develops, as well as empirical evidence and practical guidance for promoting cyber ethics education and behavioral interventions in higher education.</p>