In order to evaluate the water resources regulation scheme for the river network in the Pearl River Estuary, taking the water system of Hengqin central ditch as the research area, aiming at the problem of water transfer scale in the original regulation scheme, combined with the characteristics of Hengqin central ditch water system, the tidal characteristics of the outer river and the characteristics of water environment, the regulation scheme was optimized. The water exchange capacity was proposed as an index to evaluate the original regulation scheme and the optimized scheme. The results show that the water exchange capacity of the original regulation scheme was insufficient. After the water transfer range was increased in the optimized scheme, the half exchange period was generally shortened and the water exchange efficiency was improved, which could meet the planned water quality objectives.