In order to realize high quality electric energy for constant current regulator,Lighting constant current regulator based on a king of current source PWM rectifier was analyzed in this paper. Working principle and mathematical model of the light constant current was analyzed firstly,and solved the steady-state solution of the circuit equation by large signal model, decoupling control method based on feed forward control was designed for regulator,steady-state error of control loop can be decreased effectively, and constant current output can be realized,the harmonic content of output current and line side current can be also decreased effectively,simulated by MATLAB/SIMULINK, direct component of regulator had small ripple wave, THD in line side current was reduced from 2.71% to 1.88%, and the harmonic content of the output current from the load side is reduced from 1.24% to 0.15%. The performance of the improved type light regulator is better than that of the traditional light regulator.