Abstract: A 24 GHz low-cost millimeter wave imaging system is proposed for security inspection of hidden dangerous metal products. The system uses a low-cost 24 GHz commercial frequency-modulated continuous wave (FMCW) radar as the scanning source, synthesizes large aperture at azimuth and elevation angles, and uses a 2D cross scanning platform to image hidden objects through FMCW radar signal processing and synthetic aperture radar (SAR) processing. Low cost RF peripheral only provides single-channel IF signal by the ADC sampling quantization, all the way in the image reconstruction, this paper puts forward the single-channel ADC sampling after quantification of IF digital signal through the Hilbert transform into a complex signal, optimization for complex signal and Blackman window spectrum, then the signal sequence zero padding to minimize frequency fence effect, after adopting spatial matched filter to compensate the phase deviation, the near field imaging principle of FMCW radar is used to image the target. The improved algorithm is suitable for the low-cost radar front-end system, and the imaging system can achieve the theoretical SAR imaging resolution only by collecting only one channel IF digital signal from the ADC.