Abstract: Objective To analyze characteristics of the core social network and the roles as influencing factors on HIV-risk behaviors and to provide basis for HIV/STDs intervention among young men who have sex with men(MSM).Methods 193 eligible MSM were recruited to participate in the study by using Respondent Driven Sampling(RDS)in Hefei,Anhui,China.All were interviewed by face to face.Variables included social demographic characteristics.number of homosexual partners and sexual behaviors during the previous six months,the egocentric networks were constructed by linking together named 1 to 5 primary network members(namely,the core social networks).Results It was found that in predictive models of MSM who had at least 2 anal sexual partners in the past 6 montks：(1)MSM whose core social networks consisted of women(≥ 50%)showed that odds ratio was 0.174(95% confidence interval：0.043 to 0.705)in comparison with those MSM whose core social networks only consisted of men.(2)Proportion of the MSM's network members received coHege education reach to 50% or higher,those MSM showed that the odds ratio was 0.472(95%CI=0.236～0.947)in comparison with counter.part.(3)MSM whose network members fully supported his sex-orientation showed that the odds ratio was 2.141(95%CI=1.128～4.065)in comparison with counterpart.In the UAI predictive models during the previous 6 months：(1)MSM whose sex-orientation was fully open to his network members showed that the odds ratio was 1.955(95% CI=1.071-3.716)in comparison with counterpart.(2)MSM who didn't have sex with his social network members showed that the odds ratio was 0.239(95%CI=0.126～0.454)in comparison with counterpart.Conclusion Social networks played animportant role in dissemination of HIV-risk behaviors.This emphasizes the importance of using social networks approaches,which ate the potential resources,to control HIV among young men who have sex with men currently.