Abstract: We review and analyze the insulation and heat dissipation research of the key component high power density medium-high frequency transformer in response to the development needs of large capacity power electronic transformers. High power density presents new challenges to the solid insulation and heat dissipation performance. Firstly, the contradiction between insulation and heat dissipation during the design and application of high power density medium-high-frequency transformers is discussed. Secondly, the research progress of high-frequency insulation failure is mainly discussed, including characteristics such as insulation breakdown, partial discharge, surface discharge, and electrical tree deterioration. Then, the current research on the failure mechanism of high-frequency insulation is analyzed, including thermal breakdown, space charge effect, high-frequency conductance, and free volume effect. Finally, the research on the life of high-frequency insulation is discussed, and the influences of frequency, temperature, voltage change rate du/dt, etc. on the corona-resistant insulation life and the life model are analyzed. Based on the research advancements, the research prospects of high-frequency insulation and heat dissipation are proposed. The review research in this article is of great importance to the design and application of large-capacity power electronic transformers.