Overvoltage and insulation coordination is one of the key technologies of DC distribution network, and the research results of the coordination will play an important role in guiding the selection of the key equipment in DC distribution system. Based on the research results of traditional DC projects and the MMC-HVDC transmission projects, two insulation coordination schemes applicable to the ±10 kV DC distribution demonstration project in Shenzhen based on modular multilevel converter(MMC) are proposed considering the chracteristics of the DC distribution system. One scheme is without arrester, and the insulation levels of equipment are obtained by multiplying a bigger insulation margin. The other one is to configure a few arresters, and the insulation levels are determined based on the protection levels of the arresters. By establishing the internal over-voltage simulation model of the systems in PSCAD, the overvoltage of critical locations under typical fault conditions for different schemes are simulated and calculated, and two optional schemes of insulation level for the key equipment of the DC distribution system are ultimately determined, which provides reference for the project design.