Improving walkability in the campus environment and socio-psychological environments can promote students' mental health and subjective well-being. This study aimed to propose a theoretical model to investigate the link of perceived campus walkability (PCW) with mental health and life satisfaction (LS), and to disentangle the mediating impact of socio-psychological environments and academic performance on this relationship, while simultaneously considering the effect of the COVID-19 pandemic. We applied structural equation modeling to analyze the data collected through a questionnaire survey conducted at six universities and colleges in Yantai, China. PCW had both direct and indirect positive effects on mental health and LS. However, indirect effects are greater than direct effects. Walking attitudes, social capital, and academic performance were critical to the relationship between PCW, mental health, and LS. Academic performance had the strongest indirect effect on mental health, while social capital had the strongest indirect effect on LS. We also found that during the COVID-19 pandemic, body mass index and family income were significantly correlated with mental health and LS. The findings indicate that campus planners and policymakers should improve PCW and support the socio-psychological environment to promote students' mental and social health during situations like the COVID-19 pandemic.