Objective: To investigate the status and factors associated with commercial sexual behavior among men who have sex with men (MSM) in Shenzhen. Methods: A convenience sampling method was used to recruit MSM in Shenzhen from 2011 to 2015. Questionnaire-based interviews were conducted on a one-on-one basis. Data were collected, including socio-demographic information, HIV testing history, history of blood donation and drug abuse in the last 2 years, self-reported sexual orientation, role in homosexual behavior, and experience serving as a male sex worker and/or as a client of male sex workers. Blood samples (5 ml) were taken and tested for treponema pallidum and HIV antibodies. The rate of MSM serving as male sex workers among different age groups was analyzed using the Cochran-Armitage trend test. Factors associated with commercial sexual behavior were analyzed by univariate logistic regression and multivariate unconditional logistic regression. Results: Among the 3 040 MSM recruited, 341 (11.2%) reported having served as male sex worker. The prevalence rates of syphilis, HIV, and syphilis-HIV co-infection among all recruited MSM were 18.3% (556/3 040), 9.8% (297/3 040), and 5.1% (154/3 040), respectively. The prevalence rates of syphilis, HIV, and syphilis-HIV co-infection among those who served as male sex worker were 27.0% (92/341), 16.4% (56/341), and 8.8% (30/341), respectively, and the prevalence rates among MSM with no experience as male sex worker were 17.2% (464/2 699), 8.9% (241/2 699), and 4.6% (124/2 699), respectively. Compared with non-male sex worker MSM, male sex worker had a significantly higher prevalence rates of syphilis, HIV, and syphilis-HIV co-infection (with χ2 values of 19.41, 19.28, and 11.12, and P-values of <0.001,<0.001, 0.001, respectively). The results of the multivariate logistic regression analysis indicate that>30-year-old MSM or education level of college or above, reside in Shenzhen for 0.5-3.0 years or the living years above 3.0 years are less likely to serve as male sex worker compared with<30-year-old MSM, education level of high school or below, who reside in Shenzhen for less than 0.5 years; the OR (95%CI) values were 0.55 (0.42-0.71), 0.10 (0.06-0.14), 0.46 (0.31-0.68), and 0.23 (0.16-0.33), respectively. MSM having a monthly income of >5 000 yuan, drug abuse history, experience as male sex worker clients, and self-reported insertive and receptive anal sex behaviors were more likely to have experience serving as male sex worker compared with those having a monthly income of <3 000 yuan (OR=2.57, 95%CI: 1.85-3.57), no drug abuse history (OR=3.23, 95% CI: 2.14-4.87), no experience as male sex worker clients (OR =1.50, 95% CI: 1.04-2.15) and who engage in predominantly insertive anal sex behaviors (OR=1.77, 95% CI: 1.34-2.35). Conclusion: Age, education level, duration of residence in Shenzhen, monthly income, history of drug abuse, role in homosexual activity, and had experience commercial sex activity were associated with serving as a male sex worker among MSM. These factors need to be considered when designing syphilis/HIV prevention programs for MSM.