Thu Bon river mouth is a seasonally forced tidal inlet and periodically moving under the combined effects of hydrodynamics and morphodynamics. With the MIKE21 softwave application, the simulation of combined wave and current and sandiment transport was carried out using characterized boundary conditions of hydrodynamics. Results show that during the north moonson duration, the net sediment transport is southwards with amount of 60,000-70,000 m3/year approximately, while in the southwest moonson time, the net direction of transport is northwards with total sedimentation nearby the inlet is approximately 40,000 m3/year. In front of the river mouth the sand bars are formed to barrier. With above phenomenon, the tidal inlet is in trend to move north-south direction and sedimentation is dominated yearly except 4 months of jlood duration. Based on the simulated results, the jetty system is suggested to apply for protection of longshore sediment transport, anti-sedimentation, releasing flood water and creating favourite navigation routes.