Abstract: In this paper, an idea of the following simplification is presented, i. e. a mechanical of a fine small planar mo-tion of object grasped by a multifinger hand can be simplified into a stiffnessmass system, where the translationalstiffness and the torsional stiffness and coupling stiffness are introduced. A disturbing index is introduced to meas-ure the total effect of the disturbing force and moment excrted on the system. After analyzing the stability condi-tions of the system equilibrium state, it is considered that for a system satisfying statics equilibrium conditions andstate selection conditions and stability conditions the optimal contact state is the one with maximum disturbing in-dex. The theory of non-linear programming is adopted to solve the optimal state of the system. Finally, a numeri-cal example is given for a hand of type A3-A3-A3 to grasp an ellipsoid.