Abstract: Modular multi-level railway power regulator（MRPC） is more suitable for power quality management of traction power supply system because of its advantages of high voltage resistance grade and large compensation capacity. Due to the modular multilevel railway power regulator using more than one and a half bridge sub modules in series, and the system structure is complex, has the characteristics of multi-variable, nonlinear, strong coupling, therefore, it is difficult to establish accurate mathematical model. The traditional PI controller can only realize approximate linearization control, but based on differential geometry theory, a state feedback accurate linearization method is proposed to establish the nonlinear coordinate transformation of state variables, solve the state feedback control rate, and realize the independent decoupling control of active and reactive power of inner loop current. The simulation system was built in MATLAB/SIMULINK to simulate the actual working conditions. And compared with the double closed loop PI control, the simulation results verified the effectiveness and superiority of the strategy.