Based on one-year wave observations off the coast, this paper studies the longshore transport rate of sediment and coastline deformation of the gulf by a joint method of formula and wave mathematical model.Calculation results show that the wave dynamic condition and sediment transport direction are changed nearby Haojiang estuary after implement of the project, and as a result, siltation occurs at two ends of the bay to the west of the estuary and erosion in the middle of that; About 5 years later, a sand barrier will form between the coastline and the two islands on the west side.