A micro gripper system based on piezoelectric driver was designed for manipulating micro object with diameters of 20～40 μm. The structure parameters of the grippers were optimized using finite element analysis. The system could achieve the conversion between two fingers and three fingers, so the flexible operation of different micro objects was realized. In this paper, the relationship between the driving voltage of piezoelectric ceramics and the displacement of the endeffectors was plotted, and the driving range of the single finger was 0～41 μm. In the experimental system, the output displacement resolution of the system was 0.5 μm/V. The clamping, releasing and threedimensional model assem〖JP〗bly experiments were completed using the micro spheres which diameter were from 20 μm to 40 μm.