In this paper, a low radar cross section (RCS) tightly coupled dipole array (TCDA) based on novel dual-polarized frequency-selective polarization converter (FSPC) has been proposed. The proposed FSPC structure is comprised of a polarization conversion metasurface and a band-pass frequency selective surface, and the coding sequence of FSPC can be derived by simulated annealing algorithm to achieve simulated mono-static RCS reduction. The process of the co-design of the TCDA with FSPC is presented, and the radiation performance of the antenna array meets the design requirements. A TCDA sample and 20 × 20 FSPC elements were designed and fabricated. The measured results indicated that a significant reflection reduction from 15 GHz to 21 GHz compared with a metallic plane of the same size at the boresight, and the simulated and measured normalized radiation patterns are in good agreement.