In order to solve the problem of low efficiency and poor accuracy of the 3-D imaging algorithm using parameter estimation in the imaging mode of circular synthetic aperture radar, a 3-D imaging algorithm of parameter estimation circular SAR based on the minimum energy criterion was proposed. Firstly, the imaging scene was divided into a rough mesh with the algorithm, the method of parameter estimation was used to get the rough position of the target. Secondly, the minimum energy criterion and the fine grid method were used to get the accurate 3-D position and scattering intensity coefficient of the target. Finally, the CLEAN technology was used to eliminate the impact of estimated points and realize 3-D imaging of the scene. The simulation results show that the proposed imaging method can effectively carry out 3-D imaging of the objects under circular observation. Meanwhile, compared with the traditional algorithm, it solves the problems of low efficiency and inaccurate target estimation of the traditional algorithm, and verifies the effectiveness of the proposed algorithm.