The present disclosure provides an imaging method for a Synthetic-Aperture Radar (SAR) in a high squint mode. The method includes: perform perturbation function multiplication for an echo signal in the azimuth Doppler domain-range time domain to eliminate the dependence of an echo signal quadratic azimuth-range coupling factor on the change of a target slant range; perform reference function multiplication in the two-dimensional frequency domain, wherein the reference function is a conjugate function of a point target echo spectrum at a reference slant range; complete compensation of all phases, which do not vary with the range, of a two-dimensional spectrum through the multiplication of the two-dimensional spectrum and the reference function; rectify the differential range migration factor of the echo signal in the two-dimensional frequency domain by utilizing Chirp-Z transform, complete range migration rectification by performing convolution once and phase multiplication twice; compensate an azimuth residual phase through the azimuth phase multiplication, and perform azimuth compression to obtain a focused SAR image. The method of the present disclosure can perform highly efficient and precise imaging for high squint SAR data.