Abstract: To achieve precision motion positioning, a legged micro robot is presented based on stick-slip motion principle. The legs composed of elastic beams with spatially unequal sections are driven by the piezoelectric bimorph. A finite DOF (degree of freedom) model of the flexible leg and a dynamic model of the robot system are built. Then, according to the different characteristics of sticky state and slippage state, statics analysis of the sticky state and transient dynamics analysis of the slippage state are conducted respectively. The relations of displacement versus voltage and of resolution versus voltage are obtained. The variation of friction force and state switch process of leg end during stick-slip process are analyzed. According to analysis results, it is found that the static displacement of the base is nearly linear with driving voltage at sticky state and will step up with the increase of driving voltage. And due to the vibration of the flexible leg and the coupling between the vibration and the friction, the slip displacement of the leg end and the displacement of the base are nonlinear with the driving voltage at slippage state. Finally, a robot prototype is developed, and the resolution and displacement response are tested. The results show that the presented micro robot can achieve the motion resolution of 0.88 μm based on stick-slip motion principle.