A study on hydrogenated amorphous silicon-germanium alloys is presented. Amorphous thin films are prepared by RF magnetron cosputtering. The dependence of the optical properties and parameters and the local hydrogen bonding to the composition of a-Si1-xGex:H films (x<0.4) has been investigated. It is very important to take into account the variation of hydrogen concentration when the influence of Ge content on optical properties and parameters is considered.