Abstract: In this paper, basing on analyzing the time-frequency relationship in azimuth of Spotlight SAR, and according to the difference of the signals of spotlight SAR and strip SAR, a new method which can realize the imaging of spotlight SAR by utilizing the squint mode imaging method of strip SAR is proposed. The azimuth signal of a sub-aperture can be regarded as a sub - band of the full aperture. After imaging the spotlight SAR signal using the imaging method for squint mode strip SAR, the sub-apertures are combined. The having full aperture resolution image is recovered and the azimuth resolution is improved.