The co-phase power supply system can provide the compensation of negative-sequence current,reactive current and harmonic current and solve the problem of electrical separation in the traction network.This paper introduces the working principle of single-phase combined co-phase power supply system and train regenerative braking.By establishing a simulation model,the influence of three-phase unbalance,power factor and harmonics on co-phase power supply system and three-phase power network is analyzed in regenerative braking condition.And the effectiveness of the co-phase power supply system in solving the power quality problems without change the control strategy in regenerative braking is verified.