Abstract: A θ_xθ_yZ micropositioner is developed based on planar compliant mechanism. The static analysis is completed where only the planar deformation of each leg is taken into consideration. The effects of each leg on the mobile platform are analyzed separately. The Castigliano's theorem is utilized to derive the relationships between inputs and outputs. The relation between the displacement amplification of each planar leg and the structure dimensions is formulated. Then, the dimension parameters are optimized by means of genetic algorithm. Finally, the finite element analysis (FEA) and the experimental tests on two prototypes are accomplished. The results show that the static analysis and optimization method are reliable. The errors between the analytical model and the FEA are less than 4% while the errors between the analytical model and the experimental tests are less than 12%.