This paper proposes an imaging algorithm with adaptive aperture energy division. This method is suitable for circular synthetic aperture radar (CSAR). The algorithm is an extension of the traditional CSAR polar format algorithm (PFA). Firstly, to avoid the loss of image detail information caused by the mismatch between the aperture size and the energy distribution in the traditional self-aperture division, a method based on the aperture energy to divide the sub-aperture is proposed. Then, according to the PFA algorithm image the sub-apertures separately, and perform incoherent fusion of the imaging results to quickly obtain high-resolution imaging results. Finally, simulation results validate the feasibility of the proposed approach.