Mirror-frequency interference suppression of main-lobe clutter is of importance in PD(pulse Doppler)-radar guided missile with low-attitude down-attacking application. This paper presents a new method of main lobe mirror-frequency interference suppression based on main-lobe clutter velocity estimation and compensation of phase error between IQ channel. Theoretical analysis and simulation result show that the method has advantages of low computation and effectively suppressing the mirror-frequency components of main-lobe clutter while preserving the target frequency components that may exist in mirror-frequency area.