Abstract: It is of great significance to identify the background characteristics of soil environment in the island, especially the spatial heterogeneity of heavy metals in the soils and its potential impact on the adjacent sea areas, which is a prerequisite for the assessment of the island's ecological carrying capacity and vulnerability. In this study, Tianheng Island, an inhabited island of Shandong province, was chosen as a research object. Concentrations of five heavy metals, Cu, Ni, Cr, Pb, and Zn in the soils sampled from the island were analyzed, and the spatial heterogeneity characteristics of the five heavy metal contents were studied by using the inverse distance weighting method. Two topographical elements, slope gradient and aspect, were used to study their influence on the spatial distribution of the heavy metal contents by using geographic detectors. The potential risk sources of precipitation runoff pollution to adjacent sea areas were predicted through catchment area analysis. The result shows that the heavy metal contents on Tianheng Island did not exceed the background value of Shandong Province, in line with the Chinese cultivated land standard, except Zn slightly polluted. Based on the correlation analysis, there is no significant correlation between land use and heavy metal content, but there is a significant correlation between different vegetation distribution and heavy metal content (p<0.01). The results of geographical detector analysis showed that slope and aspect had little effect on the spatial distribution of heavy metals, and their combined effect had a nonlinear enhancement contribution to the spatial distribution of the heavy metals. Based on the analysis of the catchment area, there are many water outlets flowing into the ocean, and some catchment areas contain more heavy metals. Heavy metals on the island might cause marine pollution risks through stormy runoff, which might affect the marine aquaculture industry. It is suggested that, to the point precisely, the outlet can be combined with the hydrodynamic force for the precise governance. The research results are of important theoretical significance for improving our understanding the spatial distribution characteristics of background contents of heavy metals in the soils of inhabited islands, and for a new round of development and construction of Tianheng Island based on land and sea oriented overall planning.