Abstract: A modal beamformers design method for uniform concentric circular arrays is proposed.By deriving the expression of data model for the concentric circular arrays in circular harmonics domain,the equivalence between element-space and circular harmonics domain is established.Theoretical analysis shows minimum variance distortionless response beamformer against planarly isotropic noise field in the circular-harmonics-domain is equivalent to a phasemode beamformer for uniform concentric circular arrays.Based on this conclusion,a method for optimizing the radius of concentric circular arrays is proposed.Simulation results show the excellent performance of the proposed beamformers and the effectiveness of the optimization method.