Serious power quality and neutral sections disadvantage restrict the evolution of traditional traction power supply system. A new traction power supply system is proposed in this paper based on three-phase to single-phase converter as the key equipment in substation. This converter adopts modular multilevel converter, connects between industrial grid and feeder line without using output transformer. It transfers active power from three-phase grid isolated to one-phase traction line, and provides the frequency, phase and amplitude controlled output voltage. Then, the feeder line between different substations can be connected directly without neutral sections. The simulation verified the viability and effectiveness of the proposed system.