The limitations of traditional fossil fuels have prompted researchers to develop new renewable energy technologies. Raindrop impact energy has become a research hotspot in the field of energy harvesting due to its wide distribution and renewability, especially in the self-energy supply of microrobots. The energy harvester is installed on the robot, utilizing piezoelectric-energy-harvesting technology to achieve self-energy supply for the robot, but the efficiency of existing raindrop energy harvesters is unsatisfactory. In order to better collect the impact energy of raindrops and broaden the application of piezoelectric energy harvesters in the field of autonomous energy supply of robots, inspired by the vibration generated by raindrop excitation of plant leaves in nature, a raindrop energy harvester for autonomous energy supply for robots was proposed through the bionic leaf design, a mathematical model was established for numerical simulation analysis, and the effects of excitation position, excitation height, petiole length and excitation rate on the output performance of the harvester were analyzed. Numerical simulation and experimental test results show that the piezoelectric energy harvester has a higher output at the excitation position at the tip. The higher the excitation height of the water droplet, the higher the output voltage. Increasing the length of the petiole can significantly improve its performance output, and at the same time, the raindrop excitation rate will also affect its output to a certain extent.