In this letter, the partially thinned subarrays to be optimized by using a two‐stage random search method are presented. The cost function is defined by the side lobe blanking (SLB) cover rate and maximum peak side lobe (MPSL) and the gain over the system noise temperature (G/T). To form the subarrays, especially two subarrays are randomly selected, then 16 array elements of those subarrays are eliminated randomly to generate partially thinned subarrays. Although the G/T of the optimized subarray structure is lower by 0.07 dB/k than the reference subarray structure, the false alarm rate decreases to one‐sixth and the MPSL decreases by 1.6 dB.