Sapphire optical window which coated by metal mesh electromagnetic shielding has high transmittance in laser and infrared band,also has good electromagnetic shielding effectiveness in radar band. In order to suppress the stray light generated by the diffraction of the metal mesh in the electromagnetic shielding optical window,improve the detection distance and resolution of the optical system,and meet the needs of the new system of military photoelectric detection equipment,a metal mesh with a random ring structure is designed in this paper. A grid electromagnetic shielding optical window is used,and the diffraction characteristics of the metal mesh electromagnetic shielding optical window in the optical band and the electromagnetic shielding effectiveness in the radar band are modeled and simulated. The results show that the random ring metal grid electromagnetic shielding light window designed in this paper which has excellent diffraction uniformity and optical transmission. And the shielding efficiency in the 1～18GHz frequency range is better than 20 dB. It has excellent comprehensive performance and is expected to be used in advanced photoelectric detection equipment.