Abstract: Objective To examine the infection of HIV/sexually transmitted diseases(STDs) and reproductive tract diseases through sexual behavior in female sex workers(FSWs) during menstruation.Methods The FSWs were investigated at reproductive health services with an anonymous questionnaire survey and a semi-structured interview.The FSWs who provided sexual services during menstruation(the observation group) and who did not(the control group) were detected for human immunodeficiency virus(HIV),syphilis and other related serological tests.Results Totally 322 questionnaires were collected with 106 from the observation group and 216 from the control group.In the observation group,88.7% of the FSWs were diagnosed as STDs such as condyloma acuminatum,gonorrhea,nongonococcal urethritis (mycoplasma infection or choamydiae infection),herpes progenitalis,and syphilis,with a significantly increased prevalence compared to that of the control group(69.4%,χ²=14.332,P< 0.001).In the observation group,87.7% of the FSWs were diagnosed with correlated genital duct disease,including monilial vaginitis,infusorian vaginitis,and bacterium vaginitis,higher than that of the control group(70.8%) with a significnat difference between the two groups (χ²=11.266,P=0.001).Among the FSWs in the observation group,32.1% knew the knowledge about HIV/AIDS/STDs,lower than that of the control group(52.3%),with a significant difference between the two groups (χ²=11.740,P=0.001).No case of positive to anti-HIV antibodies was observed among the FSWs.Conclusion Sexual intercourse during menstruation can increase the risk of STDs and reproductive tract infections.HIV/AIDS/STDs knowledge dissemination and behavior intervention should be strengthened in FSWs.