In November 2020, sediment samples were collected from the Yalong Bay Qingmei Port mangrove nature reserve and the Sanya River mangrove nature reserve in Hainan Province. The present study focused on the community characteristics of marine nematodes and their influencing factors in these two mangroves. The results of the present study showed that the average abundance of marine nematodes was (80.4 ± 40.3) ind./cm² in the Qingmei Port mangrove, while it was (96.7 ± 55.6) ind./cm² in the Sanya River mangrove. In this study, the average abundance of marine nematodes in the two study mangrove wetlands was (88.5 ± 47.1) ind./cm². There were significant differences in the abundance of marine nematodes between the two mangrove wetlands. A total of 77 species of marine nematodes were identified, belonging to 56 genera, 21 families and 7 orders. The dominant genera in the Qingmei Port mangrove were Neochromadora, Terschellingia, Paramonohystera, Daptonema and Desmodora, and epigrowth feeders were the dominant feeding type. The dominant genera in the Sanya River mangrove were Terschellingia, Sabatieria, Eleutherolaimus, Parodontophora and Ptycholaimellus, and the selective deposit feeders dominated. Terschellingia dominated in both mangroves. There were spatial differences in the community structure of marine nematodes in study mangroves. Although the marine nematode communities differentiated between the two mangroves, the difference was not significant. Organic matter content and phaeophorbide content in sediments were important factors affecting the abundance and community structure of marine nematodes in Sanya River mangrove. The differences in mangrove vegetation types may affect the abundance and community structure of marine nematodes in Qingmei Port mangrove to some extent. The differences of sediment granularity characteristics, seawater pH and salinity could explain the differentiation of marine nematode communities at selected sites of the two mangrove. In addition, there are sewage project, port construction and tourism development in Qingmei Port mangrove. And there are felling, dike construction, salt pan development and wastewater discharge from shrimp ponds in Sanya River mangrove. The different pollution status in these two mangroves may also be the reason for the differences in the abundance and community structure of marine nematodes in this study.