The hydrology and sediment environments in the ocean area near the project are analyzed according to the measured data firstly.In view of the characteristics of irregular coastline,complex terrain,numerous islands of the sea area,a two-dimensional model of wave,tidal current and sediment transport is built and verified to study the tidal and sediment transport law after implementation of the first phase channel project,analyze the tidal current characteristics,cross flow in channel,annual deposition and possibility of sudden deposition under the extreme weather condition.The main conclusions are as follows.The current flow in the channel is smooth and the cross flow is not large；the annual siltation intensity ranges from 0.0 to 0.62 m/a,and the annual siltation volume is 1.773 million m3；under the extreme weather conditions,the bottom sediment is in the form of floating mud.The current flow in the channel is smooth and the dynamic conditions are strong.It is difficult for the floating mud to remain in the channel for a long time,but attention shall be paid to its short-term obstruction.