Abstract: Since the 1970s, the coastline of the southwestern Laizhou Bay has changed greatly mainly due to the reclamation activities such as salt fields, aquaculture dikes and port dam construction, which have caused the changes of the hydrodynamic environment of Laizhou Bay. In order to investigate the response of the hydrodynamic environment of the Laizhou Bay to its southwestern coastline changes during the past 50 years, the influence of the southwestern coastline changes on tidal current, tidal prism and water turnover capacity has been analyzed for three stages through two-dimensional numerical model. The results showed that the variation of flow velocity is mainly decreased in the southwestern Laizhou Bay from 1968 to 2020. The areas with large variation of velocity were mainly located in salt fields or aquaculture reclamation areas and sea areas near newly-built ports. In the past 50 years, the tidal prism of Laizhou Bay has decreased year by year. From 1968 to 2020, the spring tidal prism was reduced by 5.85%, the middle tidal prism by 7.28%, the neap tidal prism by 8.85% and the mean tidal prism by 6.47%, and reclamation is the main reason for the decrease of tidal prism. As for the overall water turnover capacity of the Laizhou Bay, it has been improved from 1968 to 2010, but there is little change between 2010 and 2020. As for the local water turnover capacity, the water turnover capacity around the port levees area was significantly reduced in 1990-2020.