The invention provides a linear frequency modulation signal sidelobe suppression method based on all-phase processing. All-phase preprocessing is performed on matching filter impact response so that all-phase matching filter frequency response is obtained; continuous echo receiving data with the same length of matching filter impact response in echo signals are selected to perform all-phase preprocessing so that the echo signals are obtained; all-phase matching filter frequency response is performed on the echo signals after all-phase preprocessing so that an all-phase pulse compression output result is obtained; and the echo receiving data are selected through sliding window with 1/4 of length of the echo receiving data before all-phase processing acting as step length, and all-phase processing and pulse compression are performed repeatedly until all the echo receiving data processed completely. Starting from the frequency domain pulse compression processing process, all-phase processing is performed on matching filter impact response and radar echo by utilizing advantages of great spectrum leakage suppression performance and phase invariance of all-phase spectrum analysis, and excellent main sidelobe performance is acquired through combination of sliding window receiving so that detection performance of radar for weak and small targets can be enhanced.