Abstract: For the purpose to evaluate the resource potential of placer deposits between the water depth of 30～100 m in the southeast water off Hainan Island, the latest data acquired by various survey methods are applied. 815 km of single channel seismic data are processed and interpreted and a huge amount of deltaic deposits since Late Pleistocene are discovered in the study area, which are favorable for the formation of placer deposits. Based on 70 surface sediment samples and 23 sediment cores collected in this area, the reserve and grades of the four valuable heavy minerals, i.e. ilmenite, zircon, rutile and monazite, are calculated, and the spatial and vertical grade changes of the four valuable heavy sand minerals revealed. The heavy minerals are dominated by zircon and monazite, followed by rutile and ilmenite and the enrichment of the valuable heavy minerals are controlled by many factors, such as the source of ore-forming materials, the type of sediments and the hydrodynamic separation during transportation. Two potential areas of useful heavy sand resources are delineated, which are 30～60 m in water depth, 1 019.19 km² in area and about 1.5 m in thickness. A conservative estimation of the potential heavy sand resources is around 4.92×10⁸ t in amount, that is valuable for further investigation.