The tidal current harmonic analysis method is used to analyze the surface，middle，and bottom current data at three continuous stations in the sea area of Liuheng island from August 6，2020 to August 21，2020. The harmonic constants of O1，K1，M2，S2，M4，MS4 of the three stations are obtained，and the tidal current ellipses of each layer are drawn. The results show that：1）The average velocity of the surface rising tide is 33~58 cm/s，and the average velocity of the ebb tide is 27~48 cm/s. The velocity direction is mainly WNW~ESE. 2）The tidal current in the sea area is reciprocating. The nature of the tidal current is mainly regular semi-diurnal tide，and the M2 sub-tide has an absolute advantage. 3）During the observation period，the residual current velocity at the surface is 8~17 cm/s，the residual current velocity of the middle layer is 8~21 cm/s，and the residual current velocity at the bottom layer is between 7~20 cm/s. The direction is WNW. 4）The maximum possible velocity occurs during the ebb tide. The surface layer can reach 149 cm/s，the middle layer can reach 120 cm/s，and the bottom layer can reach 93 cm/s method.