Objective:To exlpore high-risk sexual behavior and associated factors among men who have sex with men（MSM）though trajectory model. Methods:Totally 390 MSM were recruited with non-probability sampling method. Clinical follow-up and question-naire were carried out at 12 th

24th

36 th

48th week. MSM were divided into different subgroups through trajectory model and the highrisk sexual behaviors of different groups were described. Univariate and multivariate regression were used to analyze associated factors. Results:The subjects can be divided into high risk group（146 MSM）and low risk group（244 MSM）through trajectory model and high-risk sexual behavior times were 1.37 and 0.43 times in last two weeks

respectively. Multivariate analysis showed that age

marriage and income had statistical significant differences（P<0.05）. The younger（OR=0.95

95%CI=0.92 to 0.99）

low-income（OR=0.53

95%CI=0.34 to 0.82）and divorced/widowed（OR=3.35

95%CI=1.34 to 8.37）participants had a higher chance of entering the high risk group. Conclusion:The trajectory analysis model can directly reflect the different development paths of MSM high-risk sexual behavior. The younger

low-income and divorced/widowed participants should be focused and the publicity of HIV related knowledge should be strengthened.