Abstract: ObjectiveTo describe the status of extramarital sexual behaviors and to analyze the effects of social-cultural factors on extramarital sexual behaviors among ethnic minority migrants. MethodsA cross-sectional study on high risk sexual behaviors for human immunodeficiency virus/acquired immunodeficiency syndrome(HIV/AIDS)was conducted with a structured anonymous questionnaire survey among 291 ethnic minority migrants selected with multistage random sampling from factories,construction sites,and service establishments in Xīngyì city,Qixingguan district and Weining county,Guizhou province,during July to October,2012. Multivariate stepwise logistic regressions were performed to analyze the effects of social-cultural factors on extramarital sexual behaviors(commercial sexual behaviors or casual partner sexual behaviors). ResultsAbout 31.6 percent of the migrants reported extramarital sexual behaviors. There was a significant difference in extramarital sexual behaviors among the minority migrants of different ethnicity,sex,religion,education level,custom of visiting girls,custom of dating at a small house,custom of not following a husband,and average monthly income. Being Dong ethnic minority,being Miao ethnic minority,with average monthly income of ≥2 000 and <4 000(≥4 000)RMB Yuan,having custom of not following a husband,having custom of visiting girls,and male were positive predicatiors for extramarital sexual behaviors with the odds ratios of 10.77,7.70,2.34(5.95),3.56,2.18,and 2.57,respectively.The education level of senior college or above played a negative role with an odds ratio of 0.34.ConclusionThe prevalence of extramarital sexual behaviors was high and influenced by the social-cultural factors including ethnicity,average monthly income,custom of not following a husband,custom of visting girls,sex,and education level among ethnic minority migrants.