Abstract: The repair of leaks in high-density polyethylene (HDPE) membranes in landfills faces severe challenges due to the extremely complex internal pollutant components and the presence of highly corrosive leachate. Therefore, the development of reliable and durable repair technologies and materials is of great significance for ensuring long-term safety of the engineering. Repair technologies need to be selected based on the stage of landfill engineering and the size of the damage: thermal repair technology mainly achieves the repair of damaged areas by heating and melting the surface of the membrane, which is suitable for the construction phase before operation; targeted electrokinetic repair technology uses an electric field to drive bentonite to repair small leaks in a targeted manner, with advantages such as no excavation required and high safety, but the technology is less mature; in-situ excavation repair refers to the technique of precisely locating the membrane leaks and then repairing them, which has significant repair effects but high construction risks and is prone to secondary pollution; in-situ grouting repair involves precisely locating the membrane leaks and then injecting specific repair slurry into the leaks using a grouting machine or other pressure feeding equipment, and it has become the mainstream technology for landfills due to its advantages such as mature technology and convenient construction. In terms of repair materials, inorganic materials include cement, bentonite, clay, water glass, and fly ash; organic materials include epoxy resins, polyurethanes, and acrylates; and composite materials are combinations of different materials. Compared to inorganic and organic materials, composite materials exhibit significant effects in repairing membrane leaks due to their comprehensive performance. The current main technical bottlenecks lie in the practical application of targeted electrokinetic repair, precise positioning for grouting repair, and safety risk control for excavation repair. Future research should focus on optimizing the ratio of composite materials and improving their adaptability in the complex environment of landfills.