In this paper, we propose a new approach to ship berthing by using autonomous tugboats. This approach overcomes the nominal effectiveness problem of actuators at slow speed maneuvering to improve the ship operation in the harbor area. The proposed SMC gave us a sliding mode control law that guarantees position tracking with desired velocity in the presence of environmental disturbances. The thrust allocation problem is solved by using a redistributed pseudo-inverse (RPI) algorithm to determine the thrust and direction of each individual tugboat. The main goal of RPI method is to minimize the power supplied to tugboats and increase their controllability. The proposed approach has been simulated on a model of a supply vessel with excellent results.