To assess risk of HIV infection and its risk factors among men who have sex with men (MSM) in Beijing, China. We conducted a cross-sectional online survey in October, 2017. Inclusion criteria of participants were: aged 18 year or more; resided in Beijing; conducted homosexual activities in past six months; self-reported HIV status as negative or unclear. Demographic information, HIV test history, social media use, and high-risk sexual behaviors were collected by a self-reporting questionnaire, and a HIV risk assessment tool was used to assess HIV risk of MSM, 5 388 particpants were finally enrolled in the study. Logistic regression model was used to analyze factors associated with risk of HIV infection. Of the total 5 388 participants, most were 18-29 years old (64.35%), and the proportion of medium and high HIV risk score was 40.36%. The odds of medium and high HIV risk score among MSM who logged onto the app 1-20 times per week and>20 times per week were higher comparing with those who logged onto the app<1 time per week (1.22, 95: 1.02-1.46; 1.69, 95: 1.38-2.06, respectively); MSM who completed college or higher education had lower probability of medium and high HIV infection risk, comparing with those who only had high school education level (1.25, 95:1.09-1.43) or junior or below education level (: 1.27, 95: 1.05-1.53); MSM who did not conduct HIV test in past year had lower risk of medium and high HIV infection risk comparing with MSM who conducted HIV test in past year (0.87, 95: 0.77-0.99), and those who reported their HIV infection status unclear had higher probability of medium and high HIV infection risk than MSM who reported their HIV infection status negative (: 1.63, 95: 1.44-1.86). The proportion of MSM who were in medium and high HIV infection risk score was high in Beijing. Lower level of education, high frequency of social media use, conducted HIV test in past year, and unclear of their own HIV infection status were associated with medium and high level of HIV infection risk.