Abstract: Heavy metal pollution is a major issue of marine environmental assessment. To clarify the distribution and concentration of heavy metals (Hg, Cr, Cu, Zn, Pb, Cd and As) in seawater of mangrove areas in Wanning Lagoon, Hainan South China, 20 surface seawater samples were collected in mid-October 2022 for analysis. Comprehensive pollution evaluation method, Hakanson index, and risk quotient were used. The originations of heavy metals were traced based on correlation analysis and bidirectional stratified cluster analysis. Results show that the average contents of Hg, Cu, Pb, and Cd were 0.044, 14.975, 0.695, and 0.628 μg/L, respectively, and Cr, Zn and As were below the detection limits in all stations. In terms of heavy metal pollution status, the Laoyehai area was better than the Xiaohai area, the natural mangrove forest area was better than other areas, and the estuary area was worse than other areas. The content of Cu exceeded the benchmark and so the degree of biological risk was relatively high among all heavy metals. Heavy metals mainly come from land-based anthropogenic activities such as fishery breeding and agricultural production, as well as atmospheric subsidence of port transportation and ship emission, and some areas were affected by point-source anthropogenic activities. This study provided a reference for the protection of mangrove ecosystem around Wanning Lagoon.