Abstract: ‍ ‍Circular Synthetic Aperture Radar （Circular SAR） imaging is a synthetic aperture radar imaging technology that realizes 360 degree omnidirectional observation. The existing Circular SAR imaging algorithms have the problems of low computational efficiency as the scene expands and reduced imaging accuracy caused by the slant-range approximation， difficult to achieve real-time imaging. In this paper， a new algorithm for Circular SAR imaging is proposed. First， the echo signal in the form of spherical wave is decomposed into an integral of plane waves. Second， according to the integration， an angular filter can be constructed by virtue of the convolution theorem， which is used to eliminate the high-order phase error in the scanning angle direction. Next， the interpolation from the polar to rectangular coordinates on the filtered signal is performed to achieve decoupling of the scanning angle and wavenumber. Finally， the target focusing is achieved by 2-D inverse Fourier transform. The algorithm is verified by simulation and actual data experiments， and the comparison between the algorithm in this paper and the BP algorithm in terms of imaging quality and imaging efficiency proves that the algorithm in this paper can achieve high-efficiency imaging.