Abstract: Dielectric barrier and arc discharge under low pressures are potential risks that restrict the insulation reliability of multi-electric aircraft drive motors. partial discharge inception voltage (PDIV) test by simulating the actual electronic control stress of automobile is an important way to evaluate the insulation performance of the drive motor. The IEC standards have been applied to guide the insulation performance assessment of motors. Previous study shows that the motor that has passed the IEC standard test process may still have premature insulation failure in actual operation. First, the paper analyzes the test method used in IEC standard, and points out that the inappropriate waveform and wiring mode applied in the PDIV testing session are the main reasons for the inaccurate PDIV results. Then, the influence of the voltage waveform and wiring mode used in the test on the authenticity of PDIV test results is proved, and the improved test method is proposed. Finally, the scientific nature and effectiveness of the improved method are proved by combining the actual and simulated measurements. The results show that the improved test method can compensate the test defects in the IEC related standards, and effectively reduce the possibility of test miscalculation. This research is expected to provide practical reference for the revision of the evaluation standards of drive motor insulation system.