Abstract: In order to meet the need of all grasp for larger or small apples. A smart manipulator of three-finger with six-joint for grasp of apple was proposed. Three fingers were symmetrically fixed around circle. Each finger was with two hinge joints and driven by one piece of axial expanse artificial muscle. The equation between air pressure and grasp force was created. The elastic coefficients and preload angles of two torsion springs were obtained by global optimization. The results of calculation indicated that grasp load for larger or small apples under a setting system pressure did not damage the largest section apple without pressure feedback.