Objective To investigate the job burnout of naval officers and soldiers in hot environment, explore the impact of social support on job burnout, and analyze the mediating effect of psychological capital between them. Methods A total of 588 naval officers and soldiers stationed in hot environment were randomly selected and surveyed with self-compiled general situation questionnaires, military job burnout scale, military personnel social support scale, and positive psychological capital questionnaire. Pearson product-moment correlation analysis was used to explore the correlation between variables, multiple stepwise regression analysis was used to predict the effects of social support and psychological capital on job burnout, and a structural equation model was constructed to test the mediating effect. Results The job burnout of naval officers and soldiers in hot environment was significantly higher than that of naval officers and soldiers in the ordinary environment (P＜0.01), and the diminished achievement was the most obvious (P＜0.01). There was significant correlation between social support, psychological capital, and job burnout (all P＜0.01). Objective support, support utilization, resilience, and hope could jointly explain 35.10% of variance variability of job burnout. The mediating effect model and Bootstrap test showed that psychological capital played a partial mediating effect between social support and job burnout (χ²/df＝4.762, goodness of fit index was 0.937, adjusted goodness of fit index was 0.904, normed fit index was 0.953, relative fit index was 0.939, incremental fit index was 0.962, Tucker-Lewis index was 0.951, comparative fit index was 0.962, and root mean square error of approximation was 0.080). Conclusion In the hot environment, psychological capital partially mediates the association between social support and job burnout of the naval officers and soldiers.