Abstract: ObjectiveTo describe characteristics and influencing factors of sexual behaviors among unmarried out-of-school youths aged 15-24 years and to provide evidence for sexual and reproductive health education. MethodsTotally 296 unmarried out-of-school youths from five different work settings were sampled with stratified random sampling in Nanshan and Baoan district for a self-administered questionnaire survey on sexual and reproductive health knowledge and sexual behaviors. ResultsThe rate of self-reported sexual behavior in the youths was 47.30%,and the rate of the males(60.26%) was significantly higher than that of the females(33.79%,χ²=20.975;P<0.05).The prevalence rates of love history and masturbation history were 76.01% and 40.20% among the youths.There were 68.93% of the youths agreeing to that they would have sex under the willingness of each other.There were significant gender differences in self-reported prevalence rate of love history,masturbation history,sexual intercourse,and attitude of premarital sex (P<0.05).The average age at first sexual behavior for the youth with history of sexual intercourse was 18.49±1.93 years,and the ratio of having first sexual intercourse before age of 18 was 55.00% among the youth.There were 97.96% of the female youths having their first sexual intercouse with the lovers,sigificantly higher that of thd male youths (79.12%,χ²=9.231;P<0.05).The results of multivariate analyses showed that monthly income and attitude towards premarital sex were main influencing factors of prematial sex behavior in the males,while education and age were the main influencial factors in the female youths. ConclusionThe prevalence rate of sexual intercourse among unmarried out-of-school youths was high.Sexual and reproductive health education should be strengthened and gender differences should be considered in health education.