This paper presents a 1-bit quantization based on frequency shifted dechirping echo for vehicle-mounted synthetic aperture radar (SAR). By processing the dechirp echo with predesigned frequency shift and setting a proper sampling rate, the high-order harmonics caused by 1-bit quantization are effectively separated from the original echo. In this way, the 1-bit echoes can be range-compressed by FFT, and then a back projection (BP) algorithm can be used for imaging. The scheme is applied to image the real-measured data obtained a vehicle-mounted SAR and the effectiveness of the method is verified.