To investigate the sexual transmission behaviors among HIV-positive MSM population engaging in unprotected sexual behaviors, as well as the relationship with health conditions and partner notification. A total of 308 HIV-positive MSM participants engaged in unprotected sexual behaviors were recruited by "snowballing" sampling in Shanghai and Chengdu. The questionnaire covered such items as the time of HIV infection diagnosis, CD4⁺ T cells count, viral load, antiviral therapy, anxiety and depressive symptoms, sexual partner types and sexual behaviors in the past six months, disclosure to fixed sexual partners and casual sexual partners among others. Of the 308 participants surveyed, the report rate of those having at least one-time sexual transmission behaviors during the past 6 months was 70.1% (216/308). Participants who had primary sexual partners and casual sexual partners following their HIV infection diagnosis accounted for 89.0% (274/308) and 68.2% (210/308) respectively. Of the aforementioned participants, 59.1% (162/274) and 94.3% (198/210) respectively had not disclosed their HIV infection to primary and casual sexual partners. Of thoes who did not disclose their HIV infection to primary sexual partners, 91.9% (147/162) reported sexual transmission behaviors. Of thoes who did not disclose their HIV infection to casual sexual partners, 89.9% (178/198) continue sexual transmission. As found in a multi-factor analysis, the infection risk exposure of those with heterosexual sexual orientation and engagement in sexual transmission behaviors was six times higher than those with homosexual orientation (aOR = 5.896, 95% CI: 1.808-19.232). For those who did not, or partially disclose their HIV infection to male casual sexual partners or commercial sexual partners, the risk exposure of further transmission was 29 times and 19 times higher than those disclose it to their sexual partners (no disclosure: aOR = 28.957, 95% CI: 7.511-65.004; partial disclosure: aOR = 18.956, 95% CI: 6.995-57.417). The highest risk came from those who continue their sexual transmission behavior within six months of their HIV infection diagnosis; the lowest risk came from those continue such behavior more than one year and within two years of their diagnosis (aOR = 0.048, 95% CI: 0.033-0.788); such risk rose to some extent for those continue such behavior over two years of their diagnosis. Compared to those without antiviral therapy, participants with the therapy pose less risk in sexual transmission behaviors. More than two-thirds of HIV-positive MSM population who engage in unprotected sexual behaviors reported sexual transmission behaviors. In this regard, increasing antiviral therapy and promoting sexual partner disclosure constituted an effective strategy to minimize further transmission among HIV-positive MSM population. Intervention of sexual transmission behaviors should be addressed to those diagnosed of HIV infection within six months.