This paper deals with the optimization of subarray partition operated in large array radar.The theoretical basis of the optimal subarray partition is analyzed based on the principle of minimizing the "residual error" of excitation coefficients.The judgment basis about the contiguous characteristic of the optimal subarray partition is presented

and an innovative approach for subarray partition is proposed.Comparing with the traditional method based on clustering algorithm

the new method can decrease the "residual error" father more

and hold better beam performance.Numerical experiments are reported when the construct of the array and the feed architecture of sum and difference beams are given.Comparing research with two old methods is also presented

and the results demonstrate the efficacy of the proposed methods.