Abstract: Anhai Bay is a narrow and semi-enclosed small bay with small entrance and extending from north to south. Due to reclamation and land reclamation activities, great changes have taken place in the beach of the whole bay. Topographic maps of 1958, 1970 and 1981, 1 ∶ 5000 water depth maps of 1999, 2009 channel and remote sensing images of 2005-2018 are used to superimpose and compare the evolution characteristics of the beach of the bay in the paper. It is found that from 1958 to 2022, due to reclamation and land reclamation, the length of shoreline was reduced by 13.6 km, the area of bay was reduced by 18.40 square kilometers, and the area of beach was reduced by 13.01 square kilometers. The 0 m isobaths expanded outward, and the water depth became shallow, which caused the decrease of the tidal volume of Anhai Bay by 80.78 million cubic meters and the tidal volume by 70%. What's more, the hydrodynamic forces in the bay weaken, and the sedimentation rate in the waterway increases, which is resulting in a serious impact on the ecological environment of the bay.