Objective: To investigate the characteristics of HIV-1 molecular transmission network among HIV/AIDS patients in Zhoushan City, Zhejing Province. Methods: The newly reported HIV/AIDS cases in Zhoushan City from 2020 to 2022 were selected. Basic information was collected and whole blood samples were obtained at the initial follow-up. The pol gene sequences of HIV-1 were amplified by RT-PCR and nested-PCR. HIV-1 subtypes were identified by Neighbor-Joining phylogenetic trees. The HIV-1 molecular transmission network was built and analyzed using Cytoscape 3.6.1 software. Results: A total of 222 HIV/AIDS cases were reported in Zhoushan City from 2020 to 2022, 200 whole blood samples were collected, and 152 sequences were obtained successfully, including 122 males (80.26%), 75 cases aged 50 years and above (49.34%), 109 cases with a junior high school education or below (71.71%), and 63 cases with commercial heterosexual contact (41.45%). The main subtypes were CRF07_BC and CRF01_AE, accounting for 45.39% and 21.05%, respectively. When the threshold of genetic distance was set to 1%, 20 molecular clusters were formed in 69 cases, with a clustering rate of 45.39%. Using the molecular network constituted by reported HIV/AIDS cases in 2020 as the baseline network, there were 2 active molecular clusters with ≥5 new cases in 2022, each with 9 cases, characterized mainly by individuals aged 50 or above, with a junior high school education or below, and transmission through commercial heterosexual sex. Conclusions The predominant HIV-1 subtypes among HIV/AIDS cases in Zhoushan City are CRF07_BC and CRF01_AE. Transmission through commercial heterosexual contact among middle-aged and elderly people is a main mode of HIV transmission.