Abstract: HVDC GIS has gradually become the key equipment in DC transmission systems. Due to its characteristics of small footprint, excellent insulation performance, and high reliability, it has the most advantages for reducing the construction cost of wind power converter stations in deep sea areas. However, under long-term DC voltage, the GIS gas-solid insulation interface will exhibit unique charge accumulation phenomena, which in severe cases can cause distortion of the electric field distribution and induce surface flashover, restricting the application of GIS in ultra-high HVDC. At present, the insulation structure design of DC GIS lacks relevant theoretical basis and technical guidelines, resulting in actual equipment design usually using increased insulation distance to ensure insulation margin, failing to fully utilize the compact advantages of GIS equipment. In addition, the treatment of metal particles, the introduction of environmentally friendly insulation gas, and the criterion of charge accumulation flashover also put forward new requirements for its insulation design. In view of this, the existing research results are summarized from various aspects such as surface charge suppression, gas-solid interface electric field regulation, treatment of metal foreign objects, and new problems that need to be solved after introducing environmentally friendly insulating gases, hoping to provide reference and support for future GIS insulation structure design, practical operation and maintenance preventing flashover caused by charge accumulation.