In this paper, a metasurface with "cross-ring" shaped structure is designed, and a 2-bit coding Phase-Gradient Metasurfaces (PGMS) design is implemented. Based on the characteristics of metasurface array, a GAPSO-APS optimization algorithm combined with the improved genetic algorithm and particle swarm optimization (GAPSO) and array pattern synthesis (APS) is proposed to obtain the optimal arrangement of the metasurface coding matrix, thereby achieving significant reduction of the broadband radar scattering cross section (RCS). The simulation of the designed metasurface is carried out and compared with the metallic surface. The results show that the designed coding metasurface can achieve 10 dB RCS reduction in the frequency band from 3.1 GHz to 29.7 GHz, thus verifying the effectiveness of the designed coded metasurface in achieving RCS reduction in the wide frequency band and the effectiveness of the algorithm.