DC grid is an effective means to cope with long-distance large-capacity transmission, new energy integration and consumption, and improve power grid control flexibility. Its grid structure planning is an important basic theoretical research. This paper studies the structural characteristics of DC grids from the perspective of steady-state power flow distribution. Firstly, the DC grid power flow calculation method considering the master-slave control and droop control mode is studied. Aiming at how to describe the power flow distribution characteristics, the weighted energy entropy index of the system load rate is proposed. At the same time, based on the number of meshes, the grid structure of DC grid is classified. Taking four-terminal DC grid as an example, the influence of grid structure on power flow distribution is analyzed .Finally, based on the PSCAD/EMTDC simulation model, a 13-terminal multi-voltage DC grid model was built to verify the correctness of the influence of the grid structure on the power flow distribution.