Abstract: The tidal sand ridges at the east entrance of the Qiongzhou Strait controlled by the eastwest reciprocating current and the landform are an important resource area of sea sand in China. Based on grain size analysis of 350 seafloor samples at the east entrance of Qiongzhou Strait, the grain size characteristics of sediments in the study area are discussed and the sedimentary environment was classified. There are 17 sediment types in the study area, which are mainly sand, gravelly sand, gravelly muddy sand, muddy sandy gravel and sandy silt. Among them, sand, gravelly sand and gravelly muddy sand mainly distribute in tidal sand ridge area, where sandy silt and silty sand distribute to the east, and sandy gravel and muddy sandy gravel distribute mostly in the shallow channel. The average contents of sediment gravel, sand, silt and clay in the study area are 9.7%, 71.0%, 15.3% and 4.0%, respectively, with an average particle size of 2.15 φ and a sorting coefficient of 1.69. The sediments contain more than 95.0% sand with average particle size of less than 2.00φ, which shows good sorting. With the weakening of hydrodynamic force, the sediments gradually become finer from west to east in the study area. According to the cluster analysis, the study area can be divided into 6 types, which represent tidal sand ridges, shallow channel, bay environment, tidal sand ridge front, open continental shelf and submerged estuarine delta sedimentary environment from typeⅠto VI, respectively.