The synthesis of movement and the biomechanics are introduced into the design methodology for the development of a minimally invasive surgery (MIS) robot manipulator : compact, lightweight and close to the surgical gesture. The goal of this study is progress toward a next-generation surgical robot system that will help surgeons deliver health-care more effectively. Based on an extensive database surgical measurements, the workspace requirements were clearly defined. The pivot point constraint in MIS makes the spherical manipulator a natural candidate. The kinematic model of the proposed structure is performed and singularities are avoided. A synthesis problem is formulated and as a result the optimal link lengths of a medical robot are determined.