A novel microwave/infrared dichroic beam combiner based on a high transparent metallic mesh was proposed to achieve the coupling of microwave and infrared signals in a dual-mode Hardware-in-the-Loop(HWIL) simulation system.Analysis models of microwave reflectivity and infrared transmissivity of the microwave/infrared dichroic beam combiner were then established.To verify the feasibility of the microwave/infrared dichroic beam combiner and the effectiveness of the analysis models, a sample of microwave/infrared dichroic beam combiner was fabricated by using laser directing writing technology on a Ge substrate,and the periods of metallic mesh under perpendicular and parallel polarizations were designed as 500 μm and 400 μm respectively to minish the difference of the microwave reflectivity at different polarizations.Moreover, the microwave reflectivity of the sample in 12-18 GHz was tested in a microwave anechoic chamber and the infrared transmissivity of the sample in 10-12 μm were measured by using a Fourier infrared spectrometer.The measurement and simulation results show that the microwave reflectivity of the sample is higher than -1.5 dB, and the infrared transmissivity is 83%.It can be concluded that the high transparent metallic mesh can be used as a novel microwave/infrared dichroic beam combiner in a dual-mode HWIL simulation system.