Abstract: In view of problem that negative sequence components in unbalanced coal mine power system affect stable running of electric locomotive, and in order to satisfy control strategy of three-phase PWM rectifier, the characteristics of asymmetric signal under rotating coordinate system and the principle of enhanced notch filter were studied, and a separation method of positive and negative sequence component was presented. The rotating-coordinate system was used to transform the asymmetric signal and the enhanced adaptive notch filter was used to filter the two-times frequency signal in the method. The Matlab/Simulink simulation results show that the method can extract DC value of positive and negative sequence components in asymmetric signal precisely and quickly and can filter some harmonic waves.