Abstract: A surgical instrument comprising: an execution assembly; a control assembly connected with the execution assembly to control opening, closing, spin and deflection motions of the execution assembly; an instrument seat for mounting a transmission means, the instrument seat having a first coupling; a sterile isolation seat for mounting a sterile isolation membrane, the sterile isolation seat having a second coupling, and the sterile isolation seat being fixedly connected with the instrument seat; and a motor mounting seat for mounting a driving means, the motor mounting seat having a third coupling, and the sterile isolation seat being fixedly connected with the motor mounting seat; wherein the instrument seat is mounted on the sterile isolation seat through a cooperation of the first coupling with the second coupling, the sterile isolation seat being mounted on the motor mounting seat through a cooperation of the second coupling with the third coupling, and the first coupling, the second coupling and the third