Thin films of amorphous seleniumhave been prepared by thermal evaporation technique. The analysis proposed by Swanepoel has been successfully employed to determine the average thickness and refractive index of the filmswith high accuracy in the spectral range of 540-1050 nm. The absorption coefficient á, therefore extinction coefficient k, have been determined from the transmission spectra at the strong absorption region. The optical absorption edge is described using Tauc formula and it has been found that the transition was direct with an energy gap equal to 2.02 eV. The dispersion of the refractive index is discussed in terms of the single-oscillatorWempleÂDiDomenico model. The dispersion energy Ed and single-oscillator energy Eowere found to be 3.888 eV and 25.514 eV respectively.