Abstract: Boron carbide films were deposited on Si and Ge substrates using KrF eximer laser. Influences of laser energy, distance between the target and substrate, and bias voltage were studied. A Fourier transform infrared spectroscope and a nano-indenter were used to test the optical transmission and hardness of the samples. Furthermore, the adhesion performance of the film and substrate was tested according to the common criterion of optical films. The largest transmission of Si and Ge advanced 10% after only one surface of substrates was coated by boron carbide films. The nano-hardness of the coated substrates reached more than 3 times that of the uncoated substrates and the adhesion was also satisfactory. The results show that boron carbide films are useful as anti-reflective and protective films for optical substrates.