Background In the post-antiretroviral therapy (ART) era, HIV care has shifted towards maximizing multidimensional Health-Related Quality of Life (HRQoL), yet a "clinical-social disconnect" persists among virally suppressed patients. This study investigates the structural associations between institutional health insurance tiers and mental well-being among people living with HIV (PLWH), exploring an "Environment-First" conceptual pathway.Methods A cross-sectional observational study was conducted among 710 virally suppressed PLWH in Western China. Participants were stratified by health insurance schemes: National Free, Resident, and Urban Employee. Inverse Probability of Treatment Weighting (IPTW) was utilized to robustly balance baseline socioeconomic confounders. The multi-method analytical framework integrated Structural Equation Modeling (SEM) to examine mediation pathways and a Random Forest algorithm to evaluate variable importance.Results Generic utility instruments (EQ-5D-5L and SF-6Dv2) exhibited pronounced ceiling effects, failing to detect socioeconomic disparities, whereas the WHOQOL-HIV Environment domain demonstrated superior discriminatory power. SEM revealed a significant indirect structural pathway: the psychological advantage associated with Urban Employee insurance was predominantly explained through ameliorated environmental (Standardized β = 0.049, p = 0.009) and financial burdens, with no significant direct association with mental health (p = 0.077). Random Forest validation confirmed the Environment domain as the overwhelmingly dominant predictor of mental health (%IncMSE = 52.2), vastly outperforming clinical markers. Furthermore, subgroup analyses identified a strong "social buffering" effect, where comprehensive insurance provided the greatest marginal environmental benefits to socioeconomically vulnerable populations, particularly those with lower education (p = 0.004) and lacking spousal support (p = 0.037).Conclusions Comprehensive health insurance is structurally associated with enhanced mental well-being among PLWH, predominantly through the indirect pathway of fortifying their external environmental and financial support systems. To eliminate the persistent clinical-social disconnect, future clinical and public health strategies must transcend the traditional biomedical paradigm by integrating structural environmental interventions and targeted financial risk protection into standard HIV care.