Despite the increasing population size and exacerbating HIV/STD transmission dynamics among migrant men who have sex with men (MSM) in China, few epidemiological studies specifically explore the determinants of their high-risk profiles. This study aimed to 1) compare the sociodemographic/behavioral characteristics between migrant and local resident MSM, and 2) investigate the correlates of HIV or syphilis infection, and experience of prior HIV testing among migrant MSM in Beijing, China. A cross-sectional survey of sociodemographic characteristics and HIV-related behaviors was conducted among 3,588 HIV-negative or status-known MSM. Participants were recruited via short message services, peer referral, website advertisement, community outreach and self-participation. HIV and syphilis infection status were lab-confirmed. The HIV and syphilis prevalence among migrant MSM were 14.7% and 8.0%, respectively. Migrant MSM were more likely to be HIV-infected compared to local MSM (14.7% vs. 7.4%; aOR, 2.02; 95% CI, 1.52–2.68). Among 2,699 migrant MSM, increased likelihood of ever testing for HIV was associated with older age, living longer in Beijing, having ≥10 lifetime male sexual partners, having insertive anal sex; while being unemployed/retired and having condomless receptive anal sex were associated with a lower odds of ever testing for HIV. Being married, living longer in Beijing, ever testing for HIV and having sex with women were associated with lower likelihood of HIV; while being unemployed/retired, having higher HIV perception, having ≥ 10 lifetime male sexual partners and having condomless receptive anal sex were associated a higher HIV odds. Increased likelihood of syphilis was associated with older age, being employed, higher HIV perception, having ≥10 lifetime male sexual partners and having receptive anal sex. Migrant MSM present unique challenge to the HIV/syphilis epidemics and access to HIV care services. Our study provides implications for targeted interventions to tackle HIV/STI risks and improve HIV testing uptake among migrant MSM in China.