Abstract: The completion of the Pinglu Canal, the main channel connecting the Xijiang main river and the Beibu Gulf, can not only greatly shorten the route to the sea and reduce transportation costs, but also provide irrigation and flood drainage services for the banks of both the tributary and the main stream of the Qinjiang River. The Pinglu Canal entering the sea through the Qinjiang River can cause the runoff of the Qinjiang River to increase, and then affect the variations of salinity and silt content in the estuary and adjacent coastal waters. Based on the tidal current model FVCOM and its sediment module, the influences of the launch of the Pinglu Canal on the sediment content and salinity in Qinzhou Bay are analyzed by means of numerical simulation. The results show that with the increase in water diversion the salinity decreases significantly in the northeastern part of the Maowei Sea, with the magnitude of salinity decrease being increasing. The envelope area of the salinity reduction also expands continuously and extends gradually towards the neck of the bay. Because there is freshwater floating on the surface, the salinity reduction in the surface layer of Qinzhou Bay is significantly greater than that in the bottom layer. The high suspended sand concentration and siltation areas in Qinzhou Bay are mainly concentrated in the three channels of the Qinjiang River and the estuarine area. With the increasing in water diversion the increment in the river channels and the estuary area is significant and that in the central area of the Maowei Sea shows a small change.