The invention discloses an SAR (Synthetic Aperture Radar) imaging method based on a time-frequency rotation back projection algorithm. The method comprises the following steps that: (1) receiving an SAR echo signal; (2) carrying out de-sloping processing on the SAR echo signal; (3) carrying out time-frequency rotation on a two-dimensional time-frequency domain signal subjected to de-sloping; (4) carrying out residual phase compensation on the two-dimensional time-frequency domain signal subjected to the time-frequency rotation; (5) carrying out distance pulse pressure on the residual two-dimensional time-frequency domain signals subjected to the phase compensation; (6) calculating an echo time delay; and (7) carrying out back projection imaging on the two-dimensional time-frequency domainsignal subjected to range dimension inverse Fourier transform. By use of the method, the received SAR echo signal is subjected to the time-frequency rotation, the azimuth sampling interval of an original echo signal is compressed, an azimuth sampling point number is effectively reduced, the complexity of the back projection algorithm is lowered, and imaging efficiency is improved.