Abstract: For broadside spotlight Synthetic Aperture Radar (SAR) imaging, Polar Format Algorithm (PFA) is applied widely as a kind of general interpolation algorithm. When PFA is applied to the squinted spotlight, coordinate rotation causes azimuth spectrum uniformly resampled. A new method of interpolation for azimuth spectrum is proposed in this paper and the accurate form of azimuth spectrum interpolation is given according to the geometry of squinted spotlight. Azimuth spectrum is resampled according to the accurate form of interpolation and uniform azimuth spectrum is obtained. Then, two-dimension IFFT is implemented and high resolution squinted spotlight image is obtained. In order to validate the effectiveness, simulation and real data are processed by the proposed method. Compared with traditional interpolation method, the scope of well-focused image is increased.