Abstract: The field of robotics involves many disciplines such as mechanics, mechanics, materials, control, electronics and computers. Among them, creeping robots can work in extreme environments, which in turn can effectively reduce the risk of manual work and improve work efficiency. Therefore, creeping robots have always been the focus of research in the field of robots. Piezoelectric ceramic is a new functional ceramic material that can convert mechanical and electrical energy into each other. The inverse piezoelectric effect refers to when an electric field is applied in the polarized direction of the dielectric, these dielectrics produce mechanical deformation or mechanical pressure in a certain direction, and when the applied electric field is removed, these deformations or stresses disappear. Based on the reverse piezoelectric effect of piezoelectric ceramics, an integrated three-legged crawling robot supported by three bending cross-sectional beams is designed. We use method of theoretical mechanics to establish the overall force analysis equation for the three-legged crawling robot. Then, we use Hamilton’s principle to establish the dynamic equation of the beams (with variable cross-sections and variable angles) of the piezoelectric-driven leg, and finally obtain the complete equations which can be used to calculate resonant frequencies of the piezoelectric-driven leg of the three-legged crawling robot. More importantly, the three-legged crawling robot is designed and produced, and the influence of the different bending angle, the different driving frequency, the different load and the different driving voltage waveform on the direction and speed of motion is explored in experiments. Finally, the asymmetric driving voltage is used to make the three-legged crawling robot realize the approximate straight motion without rail and movement of left turn and right turn, realize the designed movement in three directions, and finally analyze the energy consumption of the robot. This study can provide reference for the design and test of micro-crawling robots.