Abstract: Objective To examine the prevalence of sexual behavior and its influencing factors among farmer workers. Methods Totally 820 rural-to-urban workers from 6 villages of 3 towns in Lantian county were selected with random cluster sampling and a cross-sectional survey on sexual behavior was conducted. Results Among the farmer workers, 36.3% reported premarital sex;11.7% reported extramarital sex;17.1% reported two or more sex partners.Single factor analysis revealed that the first sexual behavior of female,youth and light manual workers was earlier than male,older and heavy manual workers(P<0.001).Multivariate analysis revealed that factors influencing multiple sex partners were gender (odds ratioOR=0.36),marriage status(OR=3.35),distance from hometown(OR=1.93),age of first sexual behavior (OR=0.79),and duration of working out of home town(OR=1.02).The ratio of using condom of the workers with multiple sex partner was higher than that of with single sexual partner(P<0.05). Conclusion The prevalence of risk sexual behavior is related to gender,marital status,and type,location and duration of working among rural-to-urban farmer workers.