A high-voltage direct-current tractive power supply system of a bidirectional interactive electrified railway is provided with a plurality of traction substations. Each traction substation is provided with first transformers connected onto an alternating-current bus and a plurality of second transformers connected onto the alternating-current bus, each first transformer is connected with a high-voltage rectifier or a first high-voltage bidirectional alternating current-direct current converter, each second transformer is connected with a second high-voltage bidirectional alternating current-direct current converter, the high-voltage rectifiers or the first high-voltage bidirectional alternating current-direct current converters and the second high-voltage bidirectional alternating current-direct current converters are connected onto a high-voltage direct-current bus of the corresponding traction substation, each high-voltage direct-current bus is connected with an electric locomotive through a catenary and a steel rail, a section post connected with the corresponding high-voltage direct-current bus is arranged on the catenary of each traction substation, and a direct-current new energy system composed of an electromobile charging and discharging system, a distributed power supply and a plurality of low-voltage direct-current microgrids is arranged on the high-voltage direct-current bus between every two adjacent traction substations. Power supply reliability of the high-voltage direct-current tractive power supply system is improved.