Ge films were prepared at different deposition temperatures and ion source bias voltage using the electron beam evaporation.The infrared refractive index was obtained by spectral inversion.Results show that the refractive index becomes larger as the deposition temperature increases.The maximum refractive index at the wavelength of 4 000 nm is 4.274 with the deposition temperatures of 210 ℃.The refractive index of film decreases first and then increases as the bias voltage increases.When the ion source bias voltage is 120 V,the refiactive index of the film is the smallest.The difference in extinction coefficient of Ge films prepared by different process parameters is small.