The south to the north project(WDP) on the saltwater intrusion in the Changjiang Estuary is studied by the improved three-dimensional(3D) numerical model.The net unit width flux in the Changjiang Estuary as well as the sectional salt flux is calculated in the North Branch(NB),the South Branch(SB),the North Channel(NC),the South Channel(SC),the North Passage(NP) and the South Passage(SP),respectively.The net seaward water flux in the SB is reduced,and the net water flux spilling over from the NB to the SB is enhanced after the eastern WDP.Under the mean river discharge condition in the dry season,the net salt flux spilling over from the NB to the SB is increased by 2.09 t/s and 0.52 t/s during the spring and neap tides,respectively,due to the eastern WDP.The saltwater intrusion in the Changjiang Estuary is enhanced by the eastern WDP.Compared with that during the spring tide,the net water diversion ratio during the neap tide in the NC is smaller,and thus the enhancement of the saltwater intrusion by the eastern WDP is smaller in the NC,and larger in the NP and the SP.The tidally averaged surface salinity at the water intakes of the Dongfengxisha Reservoir,the Chenhang Reservoir and the Qingcaosha Reservoir rises both during the spring and neap tides. The south to the north project (WDP) on the saltwater intrusion in the Changjiang Estuary is studied by the improved three-dimensional (3D) numerical model. Net unit width flux in the Changjiang Estuary as well as the sectional salt flux is calculated in the North Branch (NB), the South Branch (SB), the North Channel (NC), the South Channel (SC), the North Passage (NP) and the South Passage (SP), respectively. The net seaward water flux in the SB is reduced, and the net water flux spilling over from the NB to the SB is enhanced after the eastern WDP.Under the mean river discharge condition in the dry season, the net salt flux spilling over from the NB to the SB is increased by 2.09 t / s and 0.52 t / s during the spring and neap tides, respectively, due to the eastern WDP. The saltwater intrusion in the Changjiang Estuary is enhanced by the eastern WDP. Compared with that during the spring tide, the net water diversion ratio during the neap tide in the NC is smaller, and thus the enhancement of the saltwater intrusion by the eastern WDP is smaller in the NC, and larger in the NP and the SP. tidally averaged surface salinity at the water intakes of the Dongfengxisha Reservoir, the Chenhang Reservoir and the Qingcaosha Reservoir rises both during the spring and neap tides.