Abstract: With the increase of DC load and DC power source, DC power supply system will become the future development direction of distribution system. In order to calculate the power flow distribution of the DC distribution network, the steady-state model and control method of the voltage-sourced converter are analyzed, and the unified steady-state non-ideal model of the DC-DC converter is established. Based on the above analysis, a power flow calculation method of DC distribution network based on retaining-nonlinearity algorithm is proposed. To solve the problem that the retaining-nonlinearity algorithm requires high initial value, a method using the solution of linear power flow algorithm as the initial value is proposed, which greatly reduced the number of iterations. The proposed algorithm improved the speed of power flow calculation while ensuring accuracy. Taking the 30-node DC distribution network model as an example for analysis and the results are compared with the solution of Newton-Raphson algorithm, the advantage of retaining-nonlinearity algorithm in the calculation speed is verified.