The invention relates to a negative voltage backflow DC supply system for track traffic. A negative voltage return line and a DC converter implementing negative voltage backflow are added in a conventional DC supply system, the negative voltage return line replaces a walk rail return line in the conventional DC supply system, stray currents of the conventional DC supply system and negative effects caused by overhigh potential of the walk rail relative to the earth can be greatly reduced or eliminated, loss of a supply line can be greatly reduced, and the supply distance of a DC traction substation can be raised. At the same time, the DC converter can be used as an energy storage apparatus for storing regenerative braking energy of a train, the utilization efficiency of the regenerative braking energy in the DC supply system can be raised, and the voltage of the DC supply system for track traffic can be kept stable.