Abstract: This paper expounds the accessible region of a robot finger. Analysing the matrix turbulence, we cansce that the performance of a finger isn’t all desirable at every point in the accessible region. The optimal posture of a finger is designed according to the principle of minimum condition number of a finger Jacobian. On this basis thc link parameters are properly synthesized to ensure that the finger tip is at ornear the isotropic points when the finger posture is optimal graphic simulation for a finger is given.