PDIV and PDEV of inverter-fed motor insulation under repetitive impulsive voltages should be measured according to the standards released by the International Electrotechnical Commission (IEC). A multi-channel automatic test system for that was designed by using a two-dimensional mechanical sliding table, UHF testing technology, a high-frequency pulse power supply system, high-speed broadband data acquisition device and micro-control technology, which can accurately and efficiently measure the PDIV and PDEV of inverter-fed motor insulation. Finally, PDIV and PDEV of the twisted pair samples of inverter-fed motor insulation under repetitive pulse voltage with different rise time were tested based on this system. It was found that the overvoltage caused by the short rise time affected the PDIV and PDEV test results significantly when the rise time is shorter than 100 ns. The overvoltage at the rise and fall time of the repetitive square wave voltages could be the main cause of different PDIV and PDEV results at impulsive voltages with short rise times, which were consistent with the expected results and verified the reliability of the system.