Objective: To explore the mediating role of over-commitment in the relationship between occupational stressors and job burnout, and to offer more specificevidence-based information in exploring the work related health effects of over-commitment. Methods: A total of 1994 samples from electronic manufacturing service industry were collected in Guangdong province based on self-rated questionnaire after written consent from June to July, 2015. The Effort-Reward Imbalance questionnaire and Maslach Burnout Invertory-General Survey were used for the measurement of occupational stress and job burnout. And hierarchical regression and Bootstrap test were conducted for data analysis. Results: High effort (0.28, 0.24-0.33) and low reward (-0.37, -0.42--0.33) were significantly associated with high over-commitment when gender, age and position had been controlled. Standardizedregression coefficient of effort to emotional exhaustion, depersonalization and personal accomplishment were 0.63 (95%CI: 0.54-0.71) 、0.18 (95%CI: 0.10-0.26) 、0.32 (95%CI: 0.21-0.43) , P<0.05; and standardized regression coefficient of reward to emotional exhaustion, depersonalization and personal accomplishment were-0.60 (95%CI: -0.68--0.52) 、-0.93 (95%CI: -1.01--0.86) 、-0.46 (95%CI: -0.35--0.58) , P<0.05. Bootstrap test indicated the mediation of over-commitment were statistically significant, and mediating effect ranges from 0.093 to 0.218 (P<0.05) . Conclusion: Over-commitment can mediate the relationship between occupational stressors (job effort and reward) and burnout, and the effect varies from different workingconditions.