Short-wave /long-wave infrared dichroic beam splitters take an important role in two-band infrared imaging optical systems. The choice of substrate and coating materials are discussed. Ge,ZnSe and YbF3 were chosen as film materials and ZnSe as substrate; The coating reflecting the shortwave infrared light while transmiting the longwave infrared (8-12 μm) light is analyzed,and the beam splitter is manufactured by electronic-beam evaporation. The measured reflectivity and transmittance of corresponding band are all above 93%. Such dichroic beam splitters have been successfully applied to the actual optical system.