Objective: To understand the homosexual behavior and related factors among married MSM in Mianyang city. Methods: Between January and October in 2017, a snowball sampling method was adopted to carry out cross-sectional survey through questionnaires plus HIV testing among those MSM in Mianyang city. Logistic regression model was used to analyze homosexual behaviors and related factors among married MSM under study. Statistical analysis was used by EpiData 3.1 and SPSS 19.0 software. Results: A total of 234 MSM participated in this survey. The overall rate of homosexual behavior in these married MSM appeared as 94.9% (222/234). Rate of having anal sex behavior was 94.4% (221/234) in the past 6 months, with rate of condom use as 57.9% (128/221). HIV positive rate was 8.1% (18/222). As for the motives for homosexual behavior after marriage, 87.8% (195/222) were driven by feelings of love, 12.2% (27/222) due to 'releasing pressure’. Proportion of male sex partners would include occasional sex partners (62.2%, 138/222), stable male sex partners (26.1%, 58/222) and stable boyfriends (11.7%, 26/222). Factors from logistic regression analysis showed that homosexual behaviors were related to the factors including education level of senior high school or above vs. education level of junior middle school or below (OR=3.65, 95%CI: 1.33-9.98); local residency over one year vs. the ones having local residency less than one year (OR=23.28, 95%CI:1.67-324.89); having 10 or more friends in the MSM community vs. having below 10 friends in MSM community (OR=4.15, 95%CI: 1.28-13.43); without sex pleasure with spouse vs. having sex pleasure with spouse (OR=3.25, 95%CI: 1.22-8.62); having 2 or more anal sex partners in the past 6 months vs. having less than 2 anal sex partners in the past 6 months (OR=0.28,95%CI: 0.09-0.81). Conclusions The rate of homosexual behavior and HIV positive rate were high among MSM in Mianyang city. Homosexual behaviors after marriage were influenced by multiple factors among MSM. The motives of homosexual behavior after marriage were driven by feelings of love, the related factors were education level of senior high school or above, local residency over one year, having 10 or more friends in the MSM community and without sex pleasure with spouse. As for the motives of these behaviors was caused by releasing pressure, the related factors was having more than 2 anal sex partners.