Abstract: With the large expansion of urban load,traditional Ac distribution networks are under great pressure, and DC distribution networks provides new ideas for solving these problems.In the field of DC power grids, high-voltage DC transmission and low-voltage DC microgrid have made great achievements. However, the medium-low voltage DC distribution network has just started and current research is still in the initial stage. At present, for the medium-low voltage DC distribution network, the voltage level has not formed a set of recognized serial values.This article will discuss the voltage level sequence of medium-low voltage DC distribution network,this article first listing and selecting internal and external factors that influencing the voltage levels, dividing them hierarchically, and uses expert evaluation determine the weights;Then, referring to the current basic principles of the public distribution network, a set of DC voltage series reference values are obtained by using the principle of ”geometric mean” and ”order multiples”;Next the rationality evaluation of the obtained benchmark value by the improved fuzzy comprehensive evaluation method,and the ”geometric mean” value is added to verify；Finally consider the voltage levels used in the DC projects that are currently in operation and under construction,add 48V and 1.5kV,which are the most widely used, to the voltage level sequence as special voltages to obtain the recommended values for a set of DC medium-low voltage distribution networks. Obtaining a set of DC Medium-low Voltage distribution network recommendation values, combined the AC distribution network topology and the recommended DC distribution network topology, build DC distribution network models on the MATLAB platform.In this paper,a dc-radiation topology with two voltage levels of 10kV and 400V is established first. Considering the influence of distributed energy, the 10kV bus access to centralized wind power and the 400V bus access distributed photovoltaic(pv).Subsequently, with reference to Shenzhen DC distribution network demonstration project, a ±10kV double-side DC distribution network was built.Taking into account the influence of the zero-sequence current of fault point, set up the model of ground handling must be conducted， providing a proper zero sequence current current path.By comparing the DC-side capacitor with a shunt capacitor directly grounded and a high-impedance ground-fault current and voltage change,the shunt capacitor is grounded with a high impedance to ensure that the zero-sequence current quickly decays and the DC-to-pole voltage does not drop significantly after a fault. In this paper, considering various factors that influencing the voltage as well as the principles of constraints on the basis of the developed a method to determine reasonable to determine the value of voltage grade sequence, and recommends a set of low voltage dc power voltage sequence value: 380 v, 750 v, 1.5 kV, 3 kV, 10 kV, 24 kV, 48 kV. In this paper, considering various factors influencing the voltage as well as the principles of constraints on the basis of the developed a method to determine reasonable to determine the value of voltage grade sequence. It also recommends a set of voltage sequence values for medium-low voltage DC distribution networks:380V,750V,1.5kV,3kV,10kV,24kV,48kV.In the part of model analysis, whether or not the model is compared with the theoretical analysis mainly through the power flow calculation comparison model, thus verifying the correctness and rationality of the model