<p>A resilient psychological state is essential for students. Understanding the mental health landscape of college students in the post-pandemic context, and examining the associated determinants, lay the theoretical groundwork for ideological and political education in higher education institutions. This study collected mental health data from 3,288 students enrolled in nine private undergraduate universities in Yunnan Province during three distinct time periods, namely before the epidemic, during the epidemic, and after the epidemic, with the aim of analyzing both the short-term and long-term effects of the epidemic on college students’ mental health. To accurately assess the mental health of college students in the post-pandemic period, this study applies normalized power prior to merging pandemic-era data with post-pandemic data, thereby estimating the ability parameters of the item response theory model. The estimated value of this parameter provides a theoretical basis for evaluating the mental health status. Using this framework, the research also examines the determinants of mental health. The results indicate that: (1) the integration of pandemic and post-pandemic data yields a more precise evaluation of mental health than post-pandemic data alone; (2) although the mental health of college students has improved post-pandemic compared to the pandemic period, it still falls short of pre-pandemic levels; (3) factors such as personality, academic stress, challenges in intersexual interactions, satisfaction with one’s major, peer relationships, family relationships, teacher-student interactions, and family structure significantly affect mental health.</p>