In this paper, Weizhou Island in Beihai, Guangxi was selected as the study area to investigate the spatial distribution of selenium (Se) in volcanic soil under subtropical environment and to explore its influencing mechanism. A total of 106 topsoil samples and 16 parent material samples were collected with gridding design and the content and distribution of soil Se and their relationships with parent materials and soil other properties were analyzed. The results showed that the total Se in the topsoils of Weizhou Island ranged from 0.005 to 0.567 mg/kg with a mean of 0.287 mg/kg, and 70.87% of the total island area was covered with Se-sufficient and Se-rich soils. The contents of Se various forms in the topsoils of Weizhou Island were as follows:residual (78.06%) > organic compound (10.58%) > acid soluble (7.76%) > exchangeable (2.86%) > water soluble (0.74%). Total Se content of the different parent rocks varied significantly, highest in volcaniclastic rocks, followed by basalt and beach sediments with biological debris. The variation of total Se content in parent rocks and their corresponding soils were well matched, and Se content in the soil weathered was highest in volcaniclastic rock, then followed by basalt and beach sediments with biological debris. Soil Se enrichment of volcanic rocks was mainly attributed to the inheritance of the high background Se content of volcanic rocks, and Se was easily absorbed by Fe₂O₃, Al₂O₃ and OM (organic matter) in volcanic soils during epigenetic evolution. Se-rich soil formed by the weathering of volcanic rocks is of positive significance for the agricultural exploitation of island land resources.