Cervical laminectomy is a kind of clinical surgery mainly used for decompression of a cervical vertebrate. Because of the limited space of the cervical vertebrate, this surgery requires surgeons to operate in a higher degree of accuracy. A robot-assisted surgery can always achieve good accuracy by virtue of precise positioning and operation of the robot, and a parallel robot can perform better accuracy due to its mechanism feature. A 6-RSS has a more concise structure and lower mass of moving parts than other types of parallel robots, thus it performs better in human-machine interaction which could guarantee precise operations of surgeons. But kinematic analysis of a 6-RSS parallel robot is normally more complicated than other types. In this paper, the theoretical mechanism model of the 6-RSS parallel robot was built and coordinates were defined. The kinematic model was derived based on the closed-loop kinematic chain. The dexterity indices were analyzed to facilitate the design process of the robot.