Objective:To explore the moderating and mediating effects of psychological capital in the associations of job monotony and depressive symptoms.Methods:A convenient sampling method was used to sample 1 473 workers from a natural gas field in southwest China in October 2018.The sociodemographic characteristics, job monotony scale, PsyCap questionnaire and center of epidemiological survey, depression scale(CES-D) were conducted.Data were analyzed by SPSS 22.0 and Process v3.2 softwares.The statistical methods included t-test, one-way ANOVA, χ2 test, partial correlation analysis, multivariate regression analysis or Bootstrap method. Results:A total of 323 workers with depressive symptoms were detected, with a detection rate of 21.9%(323/1 473). The correlation analysis results showed that job monotony (13.67±1.38) was negatively correlated with self-efficacy (25.81±4.56), hope(25.91±4.55), resilience (26.80±3.80) and optimism (24.56±3.17) ( r=-0.26, -0.38, -0.36, -0.42 respectively, all P<0.01), and positively correlated with depressive symptoms ( r=0.50, P<0.01). Self-efficacy ( r=-0.38, P<0.05), hope ( r=-0.44, P<0.05), resilience ( r=-0.43, P<0.01) and optimism ( r=-0.47, P<0.01) were negatively correlated with depressive symptoms.The multivariate regression analysis results showed that self-efficacy and optimism had moderating effects on the associations of job monotony and depressive symptoms (both P<0.05), while hope and resilience had no moderating effects on the associations of job monotony and depressive symptoms (both P>0.05). The mediating effect test results showed that self-efficacy, hope, resilience and optimism played partial mediating roles in the associations of job monotony and depressive symptoms (all P<0.01), and the mediating effects were 0.139, 0.304, 0.232 and 0.339 respectively, and the proportion of mediating effect value to total effect was 12.2%, 23.3%, 18.8% and 25.3% respectively. Conclusion:Self-efficacy and optimism have moderating and mediating effects on the associations of job monotony and depressive symptoms, while hope and resilience have only mediating effects on the relationship between job monotony and depressive symptoms.