For high squint mode spotlight Synthetic aperture radar (SAR) system without dechirp-on-receive function, a new imaging algorithm and the real-time processor implementation are presented. In this algorithm, high squint mode imaging processing is treated as broadside mode processing with special motion compensation. After the fast time delay correction and the phase compensation to echo data in azimuth time domain, conventional range Doppler method for broadside mode is applied to accomplish range curvature correction. Then, azimuth compression is achieved by azimuth scaling and Spectrum analysis (SPECAN) with non-uniform interpolation. Based on this algorithm, a practical real-time imaging processor is introduced. The effectiveness of the algorithm and the real-time processor is validated by point target simulations and real-time imaging result of real raw data.