Abstract: As the main channel connecting the Xijiang shipping trunk and the Beibu Gulf, the completion of the Pinglu Canal not only greatly shortens the route to the sea and reduces transportation costs, but also provides irrigation and flood drainage services for both banks of the Qinjiang River. The Pinglu Canal enters the sea through the Qinjiang River, which will increase the runoff of the Qinjiang River, and then affect the variation of salinity and sediment content in the estuary and adjacent coastal waters. Based on the FVCOM tidal current model and its sediment module, this study uses numerical simulation to analyze the influence of the launch of the Pinglu Canal on the sediment and salinity of Qinzhou Bay. The results show that with water diversion increasing, the salinity in the northeastern Maowei Sea decreases significantly, meanwhile envelope areas of salinity reduction also expand, and gradually reaching the neck of the bay. The salinity reduction rate of the surface layer in Qinzhou Bay is significantly greater than that of the bottom layer due to the fresh flushing water on the surface. Suspended sand and silt concentrations are highest in the three channels and estuarine areas of the Qinjiang River, and during water diversion, the increase in the river channel and estuarine areas is obvious, while the center of the Maowei Sea varies moderately.