To meet the low electromagnetic scattering requirements of optical instrument windows, a metal microstructure model based on Voronoi diagrams is employed, arranging the metasurface structures in a checkerboard array. This design achieves effective reduction of Radar Cross-Section (RCS) while satisfying the transparency and imaging quality requirements of the instrument windows. Experiments shows that the checkerboard metasurface without transparentizing could achieve more than 10 dB RCS reduction in the frequency band of 11.6～17.9 GHz, and the phase response of the metasurface unit remains consistent before and after transparentizing. The designed transparent RCS-reducing metasurface has high light transmittance, can uniformly diffract stray light distribution, and possesses the characteristic of wideband RCS reduction. The research results provide a new idea for the design of low-RCS transparent windows.