Abstract: Based on the one-year measured tide data of Hainan Hongtang bay tide level gauging station from March 2016 to March 2017 and the complete measured tide data of spring tide, moderate tide and neap tide of 8 temporary stations from August 9 to August 20 in 2016 and 2017, the skewness and complex analysis method are used to study the tidal characteristics and tidal asymmetry in the Hongtang bay and analyse the distribution characteristics and mechanism of the tidal asymmetry in the adjacent waters of the Hongtang bay. The analysis results show that, as an open arc bay, the Hongtang bay sea area is an irregular diurnal tide area dominated by astronomical tides. The amplitude of the main tidal constituents K₁, O₁ and M₂ decreases slightly from shore to sea, and the tidal component epoch gradually increases from the east to the west. The annual tidal asymmetry is dominated by ebb tide. The tidal asymmetry is mainly controlled by the interaction of K₁-O₁-M₂ constituent, the short time scale fluctuates during the tidal period with its interaction, and the long time scale is subject to the tidal interaction between K₁ and S₂, which presents a semiannual periodic change; in space, it gradually reduces from the shore to the sea and from the west to the east, the variation within the bay with similar water depth is smaller and has obvious difference from the bay outside.In open arc bays, the tidal asymmetry is affected by the interaction between different astronomical tides in time and controlled by topographic factors in space; and the tidal asymmetry is stronger with a shorter distance to the shore, steep slope and shallow water depth.