In view of the high-frequency withstand requirements of insulation materials for high-frequency transformers in smart grid applications, this paper takes epoxy resin as the research object to explore its breakdown characteristics under sine wave, monopole and bipolar wave voltages. By building a high-frequency breakdown test platform, the breakdown voltage and current parameters under different waveform and frequency conditions were tested, and the influence of voltage waveform and frequency on the breakdown behavior of epoxy insulation was analyzed. The results show that the epoxy resin breakdown field strength (Eb) is the highest and the breakdown point area is the largest under the unipolar square wave, and the Eb is the lowest and the breakdown point area is the smallest under the sine wave; Under the condition of 20 °C/10 kHz, the Eb of bipolar square wave is 13.3% lower than that of sine wave and 32.6% lower than that of unipolar square wave; Under different waveforms, Eb showed a downward trend with the increase of frequency. The research results can provide theoretical and experimental support for the insulation design and reliability improvement of high-power solid-state transformer.