To investigate the electrical erosion mechanism of drive motor bearings, a simulation study was conducted to examine the influence of micro-bubbles in the lubricating oil film on the electrical breakdown process. The 6208 deep groove ball bearing was taken as the research object. A theoretical model and a transient electric field simulation model for oil film breakdown containing bubbles were established. The electric field distribution and breakdown process under bubble conditions were analyzed, and the gain effects of bubble radius, location, and quantity on breakdown characteristics were quantified. The results show that local electric field distortion is induced by bubbles, with the maximum field strength reaching 1.6×10? V/m. The breakdown time is shortened by 13.1% compared to bubble-free conditions. The electric field distortion is enhanced by increasing bubble radius, reducing the bubble–electrode distance, or raising bubble number, which significantly reduces the insulating strength of the oil film and accelerates the breakdown process. The gain mechanism of micro-bubbles on the electrical erosion behavior of bearing oil films is revealed, providing a theoretical basis for improving the reliability of drive motors.