Abstract: In order to obtain the grain size distribution characteristics and hydrodynamics of surface sediments in Sanya area and to study the indicative significance of sedimentary environment, a total of 328 surface sediments samples were collected and five fixed-point ocean current observations were completed in the coastal waters of Sanya during the 1:50000 comprehensive geological survey in this area from 2015 to 2016.The results show that the types of sediments in the study area are mainly clayey silty sand, sand, sandy silty sand, gravelly sand, silty sand and silty sand, with the mean size 0.22~7.37φ, among which clayey silty sand is the most important.The grain size transport trend indicates that there are an erosion-deposition trend in some sectors along the coastline, offshore transport of the Maozhou island and multiple deposition centers in the south of the study area.The results show that there exists a reciprocating current in the study area, the direction of high tide is northwest, the direction of ebb tide is southeast, and the direction of residual current is southeast.Based on the principal component analysis and cluster analysis, according to the hydrodynamic, provenance and topographic factors as well as their interactions, the study area is divided into three types of sedimentary environments.This division way can reveal the difference in the sedimentary environments under different controlling factors.The results of the study can provide a scientific basis for ecological environmental protection and marine engineering construction in Sanya.