An improved Monte Carlo sampling method called probability circle sampling based on the distributed generation probability model is presented. The power supply capability indexes of DC power distribution network were constructed and the multi objective function of the DC power supply capacity is proposed. The Delphi method and judgment matrix are used to analyze the index qualitatively and quantitatively prior to finally optimizing the solution with an improved genetic algorithm. In the calculation example

the DC distribution network of radial type

ring type and mesh type are calculated and compared at different permeability rates of DG. The feasibility of the proposed method is verified and considered useful as a reference for research on power supply capability of DC distribution network in the future.