The invention belongs to the radar communication technology field and particularly relates to a radar LFM composite waveform design method which has properties of Doppler tolerance, low interception probability characteristic and low relevant sidelobe characteristic and is for motion target information acquisition. The radar LFM composite waveform design method is in combination with a low relevant sidelobe waveform design method and an LFM noise waveform design concept, an LFM composite waveform mathematics model is constructed in a phase weight mode, and relevant sidelobe template vectors are introduced to construct a corresponding target function; phase constraint and constant modulus constraint conditions are analyzed, an iteration spectral approximation relaxed projection phase correction algorithm framework is constructed, LFM composite waveform optimization output programmed steps are provided, iteration spectral approximation relaxed projection phase correction constant modulus LFM composite waveform coding design concepts as described are employed, and the low relevant sidelobe characteristic and the low interception probability characteristic of waveforms can be relatively improved. The method further has properties of high efficiency, small time consumption and good robustness, and the method is more suitable for LFM composite waveform online design.