Thin films with thickness 100 nm of Ge10+xSe40Te50-x (x ranging from 0.0 to 16.65 at.%) were formed by vacuum deposition at 1.33 x 10(-4) Pa. The change in electrical resistivity of the films has been measured using coplanar method. The measurements have been carried out in a temperature range between 300 and 142 K. The values of the electrical activation energy lie in the range of 0.18-0.38 eV. The optical absorption behavior of these ternary thin films were studied from the reflection and transmission. The optical band gap was found to be in the range of 0.90-1.11 eV. and arose from indirect transitions. On the other hand, the width of the band tail E-e was found in the range 0.19-0.32 eV. and exhibits opposite behavior. This behavior is believed to be associated with a defected bond of Te-Te and a cohesive energy (CE).