In order to meet design requirements in minimally invasive surgery (MIS), it is necessary to conduct basic operations in the narrow working space. Taking a grasper for example, a 4DOF MIS instrument driven by servo motors and transmitted by cables is designed. The design of the end of surgical instrument driven by cables is suitable for long-distance transmission, which improves dexterity of the surgical instrument working in narrow space. The mechanism principle including the wrist, graspers and shaft rolling are described. Kinematic coupling between the wrist and grasper are analyzed. Prototype of the surgical instrument is presented. This instrument prototype can be applied in most MIS operations.