Recently, the number of robot-assisted orthopaedic systems has increased. As one of the backgrounds, it is considered that error between plan and result of bone cutting is not constant because of the individual surgeon skill. The authors have been developing a bone cutting robot which has 7 degrees of freedom. A prototype of the total system for minimal invasive knee arthroplasty surgery including preoperative planning system and registration system has been implemented. In this paper, details of the minimal invasive knee arthroplasty surgery system and each function contained in this system are described.