Based on the impact function of Hertz contact theory, gear contact was set up, multi-flexible body dynamics models of healthy, mild, moderate and severe gear pitting were established and simulated, and vibration response of planetary gear in time-frequency domain under different pitting conditions was analyzed. The vibration test platform of planetary gear box was built to obtain vibration response signals of planetary gear and verify the correctness and rationality of multi-flexible body dynamics model of planetary gear pitting. The morphology evolution process of planetary gear transmission tooth surface pitting corrosion was studied. The results show that the effective value and peak-peak value of vibration velocity in Y direction increase with the increase of pitting complexity. Obvious edge frequency signals appear in vibration velocity and acceleration of the slightly eroded model, and the experimental results are basically consistent with the simulation.