Based on the historical monitoring data from 1960 to 2017, the evolution of chloride concentration in the Dongping Lake was analyzed, and the mechanism of chloride concentration change was discussed. The results show that chloride concentration in the Dongping Lake has been on the rise since 1960, especially since November 2015 after the implementation of the east route of the South-to-North Water Diversion Project. The chloride concentration decreases significantly due to heavy rainfall during the flood season. Before the implementation of the east route of the South-to-North Water Diversion Project, the chloride concentration was mainly affected by the inflow river, saline-alkali soil and shallow groundwater, and after the water diversion, it was mainly affected by saline-alkali soil and shallow groundwater. Therefore, by rebuilding or expanding the salt drainage ditch and cut-off ditch, adding anti-seepage and slope stabilization project, and controlling the pool level of the Dongping Lake, etc. , it is safe as an important hub for the east route of the South-to-North Water Transfer Project and an important water source for the West-to-East Water Transfer Project in Shandong Province.