Due to different oriented diamond films having different properties, in this paper optical and electrical properties of different oriented diamond films have been investigated. The measured results indicate diamond films are of high quality and the properties of the (001)-oriented diamond film are better than those of the (111)-oriented one. Refractive index and extinction coefficient of (001)-oriented diamond film in the wavelength range of 2.5-12.5 mu m is 2.391 and in the order of 10(-5), respectively. And for the (111)-oriented one it is 2.375 and in the order of 10(-4). The dark current of the (001)-oriented diamond film is 33.7 nA under an applied electric field of 100 kV/cm. The resistivity of the (001)-oriented diamond film obtained is about 2.33 x 10(10) Omega cm. The current of (001)-oriented diamond film is almost no change with the time testing. (c) 2005 Elsevier B.V. All rights reserved.