Abstract：The characteristics and influence factors of the longitudinal stability of subsea tunnel with long-distance，high water pressure and large diameter are analyzed；and taking a certain project for example，a study on channel dredging as a new and important influence factor is carried out. Combined with the characteristics，techniques and working procedure of channel dredging，numerical simulation method with a large-scale model with 2.4 km long tunnel structure and seabed stratum is performed. The relations and influences of the channel dredging depth，the dredging working procedure，the alluvium thickness，etc. are presented on structure longitudinal stability，such as deformation and stress. Then，some conclusions of the control function from channel dredging depth to tunnel structure stability are drawn；and a nonlinear relation between dredging depth and structure transmutation and stress is achieved. It can be seen that tunnel longitudinal transmutation is obvious when channel-dredging depth is larger than 7 m. Also，it is pointed out that the control index of channel dredging depth and the layout project of channel dredging should be optimized. Finally，the reinforcing method of the shield tunnel structure and the surrounding stratum is given to guarantee the structure stability. The primary research results have some references to the proper layout and design of the subsea tunnel；meanwhile，more detailed research is also needed in the future.
