Gas insulated line (GIL) occupies an increasing proportion in the transmission system. The promotion of DC GIL can improve the existing DC transmission mode, and has a very strong economic benefits. Compared with AC GIL, the major technical difficulties and differences of DC GIL are insulation issues. Studies on DC GIL insulation issues are helpful to its operation, maintenance, and life prediction.Domestic and foreign researches on DC GIL are widely introduced from two aspects: the overall insulation design and internal partial discharge detection. It can provide a better cognition and reference for further study on DC GIL insulation problems.