Abstract: Objective To understand the influencing factors and genotypes of hepatitis C virus infection among drug users in Shanghai compulsory detoxification center, so as to provide evidence for behavior intervention and clinical treatment. Methods A cross-sectional study was conducted with 734 drug users entering the detoxification center for the first addiction from May to July 2015. Field investigation was used to explore the influencing factors, and the nested reverse transcription-polymerase chain reaction (RT-PCR)was conducted to identify the genotype. The HCV genotype and the regional distribution characteristics were also investigated. Results HCV RNA in 236 of 734 drug addicts under compulsory rehabilitation were positive, and the positive rate was 32.2%. Multivariate unconditional Logistic regression analysis showed that the drug-use time(OR_5-year=2.79,95% CI:1.64-4.75;OR_10-year=9.37,95% CI:5.30-16.54;OR_{15-25 year}=11.22,95% CI:6.26-20.01), heroin use(OR=2.02,95% CI:1.32-3.10)and injection drug-use(OR=6.62,95% CI:4.41-9.94) were risk factors of HCV infection.The education with college and above was the protective factor(OR=0.11,95% CI:0.02-0.63).In 236 drug users with HCV RNA-positive, the predominant subtypes were 3a(24.1%),6a(20.2%) and 1b(19.5%), meanwhile subtypes of 3b, 6n, 1a, 2a, 2b and 6e were also identified. Generally, the regional distribution of HCV genotype was disperse. Conclusions Drug-use time, heroin use and injection drug-use are major risk factors of HCV infection, and the subtype of 3a and 6a are the predominant subtypes.