Abstract: Epoxy resin composite insulating materials are widely used in high-voltage transmission and transformation equipment, power module encapsulation, and other fields due to their excellent electrical insulation, mechanical stability, and process adaptability. However, the incorporation of metal inserts and fiber-reinforced phases within composite materials inevitably creates heterogeneous interfaces with the epoxy resin. Under multi-field coupling of electrical, thermal, mechanical, and environmental factors, these interfaces become a critical weak point that limits the long-term service reliability of the equipment. This paper systematically reviews the failure mechanisms of typical epoxy resin-metal and epoxy resin-fiber heterogeneous interfaces in transmission and transformation equipment, with a focus on analyzing the impact of electromechanical property mismatch, the effects of humid-heat environments, and space charge accumulation on interface damage evolution. It reveals the development process of heterogeneous interface defects from initiation and growth to the eventual triggering of overall insulation failure. Based on this, the paper summarizes recent strategies for inhibiting interface failure in epoxy resin composites. It discusses the research progress in improving interface reliability from the perspectives of interface property regulation, matrix design, and process parameter optimization. The paper also outlines future research directions for interface property regulation.