By analyzing the mathematical model of the three-phase inverter power of electric locomotive, the coupling relationship between the system variables of the three-phase inverter power in the two-phase synchronous rotation ,d,-,q, coordinate system was revealed. A double closed-loop decoupling control strategy feed forward the output voltage and load current of the inverter was introduced, which realized the linear decoupling control of the three-phase inverter. In addition, the design of the double closed-loop control strategy and the parameters of the post output filter were also studied, and an engineering design method with strong practicability was put forward, which was validated by simulation and prototype test.