Abstract: Objective To estimate HIV prevalence and number of people living with HIV/AIDS (PLHA) in Zhejiang, and explore appropriate methods for epidemic estimation. Methods The data on population size affected by AIDS and HIV infection rate were collected in all the 11 prefectures of Zhejiang. And then workbook method was used to estimate the epidemic of HIV/AIDS in Zhejiang. Results In 2015, the estimated number of PLHA was 20 902 (15 439-26 365), the estimated number of PLHA in men who have sex with men (MSM) was 10 567 (7 699-13 435), in which 35.2% were distributed in urban area and 15.4% in rural area and the estimated number of PLHA in people with heterosexual behaviors was 9 745 (7 214-12 277), in which those involved in commercial sex accounted for 27.1% and in non-commercial sex accounted for 19.4%. The proportions of HIV infections caused by injecting drug use, blood transmission, mother to child transmission were only 2.1%, 0.4% and 0.3%, respectively. The overall HIV prevalence was estimated to be 0.038% (0.028%-0.048%), but the area specific differences were obvious. Conclusion Workbook method is suitable for the HIV/AIDS epidemic estimation, and the estimation results can be used to facilitate the prevention and control of AIDS in Zhejiang.