The invention discloses a direct-current traction power supply system based on a distributed power supply. More than two traction substations used for providing direct-current electric energy for an electric locomotive are arranged, and multiple transformers connected to alternative-current buses are arranged on the traction substations. The output sides of the transformers are correspondingly connected with rectifiers, wherein the output sides of the rectifiers are connected with direct-current buses located on the traction substations. The positive electrodes and the negative electrodes of the direct-current buses are correspondingly connected with contact nets and steel rails. The positive electrode and the negative electrode of the electric locomotive are correspondingly connected with the contact nets and the steel rails. The contact nets of adjacent traction substations are connected with partition places, and the two ends of the partition places are connected with the positive electrodes of the corresponding direct-current buses, and direct-current new energy systems formed by electric vehicle charging and discharging units and distributed power units are arranged on the direct-current buses between two adjacent traction substations. The direct-current new energy systems are connected with direct-current buses of two adjacent traction substations, and a direct-current annular micro-grid is formed in one power supply zone. Reliability of the direct-current traction power supply system is improved.