Abstract: Objective To investigate the prevalence and influencing factors of depression among workers in small and medium-sized enterprises in Zhongshan city and to provide a reference for the development of prevention and intervention measures.Methods A questionnaire survey was performed in 4 500 production workers selected with multistage random sampling from 54 small and medium-sized manufacturing enterprises(with the employees less than 2 000) in Zhongshan city.A questionnaire about social demographic characteristics and general health behaviors and the Center for Epidemiological Survey Depression Scale were adopted in the survey.Results A total of 3 300 valid questionnaires(70.1％ from male workers) were collected and the effective response rate was 73.3%.The incidence of depressive symptoms in the workers was 22.7%.There were significant associations between depression and sex,marital status,education level,monthly income,smoking status,regular physical exercise,and the type of the enterprise by univariate analysis(P<0.05 for all).Ordinal logistic regression model analysis revealed that risk factors for depression symptoms in the workers were enterprise type(odds ratioORfor private enterprise=1.76,95% confidence interval 95%CI=1.38-2.27; OR for Hong Kong-invested enterprise=1.64,95%CI=1.31-2.06),lower income(OR=2.36,95%CI=1.41-3.92) and smoking(OR=1.30,95%CI=1.07-1.56) and protective factors were lower education level(OR=0.79,95%CI=0.64-0.96) and physical activity(OR=0.69,95%CI=0.58-0.82).Conclusion Depressive symptoms are influenced by enterprise type,education level,income and health behaviors such as smoking and physical exercise among workers in small and medium-sized enterprises.