Recently, robotic systems are widely used in surgery, due to their characteristics such as having high precision, being tireless and making no mistakes. They are especially suitable for operation on hard tissue, as the bone is stationary and does not change shape and therefore preoperative planning of the system is much more straightforward. Nevertheless, proposed robotic systems for surgery on skull bone are still in the research stage. In this study, by considering the requirements of craniotomy surgery, a Remote Center of Motion spherical mechanism is used in design and prototyping of a surgical system. The kinematic equations and Jacobian of the mechanism are calculated analytically and later verified through software simulation. Detailed design and force analysis helped selection and use of appropriate AC servo motors for actuation. An aluminum prototype is fabricated out of CNC machined parts. Performance of different connection methods between PC and the robot were tested and a combination of them is proposed for higher reliability and speed. Finally, a software library is generated in LabVIEW environment to simplify the connection with servo motors and utilization and control of the robotic system.