Abstract: The VSC-HVDC transmission of offshore wind power has become an important way for wind power consumption.Direct current gas insulated switchgear （DC GIS） is used for offshore wind power converter platforms,which could reduce the overall platform volume and equipment cost of offshore converter stations,and reduce the operation and maintenance costs of offshore equipment.The overvoltage and insulation coordination of±550 kV DC GIS for offshore wind power have been studied.Firstly,the structure and parameters of VSC-HVDC system are studied.The control and protection strategies,and the configuration of surge arrester are given.Then,the maximum overvoltage level is obtained through the simulation.The DC pole line overvoltage of faulty pole and non-faulty pole under different operation modes are analyzed.Finally,the parameters of the arrester in±550 kV DC GIS and the insulation level requirements of the±550 kV DC GIS are given.