In the fundamental absorption region, near normal incidence reflectance Rand transmittance T measurements can provide information about optical properties of thin films [1] . Temperature dependent optical properties of p - , i - , n - layers of a-Si:H films have been studied. The behavior of reflectance R and transmittance T as a function of temperature of a-Si:H thin films is analyzed. From temperature dependence of Rand T the temperature dependence of the absorption coefficent «(I.) is calculated using Hishikawa relation. From the temperature dependent absorption coefficient, the variation of the optical energy gap of the films with temperature is determined. Finally its effect on solar cell applications is discussed