CuIn1-xGaxSe2 (CIGS) is a promising direct bandgap semiconductor material for developing a new generation of highefficiency and lowcost thin film solar cells due to its variable bandgap structure and high absorption coefficient in visible range. In this paper, a series of CIGS thin films were fabricated by combination of DC sputtering and selenizing processes. The effects of the sputtering power for deposition of CuIn1-xGax (CIG) metal precursors and substrates on the microstructures and optical properties of the CIGS films were investigated. It was found that the film, deposited at 50W sputtering power onto Mocoated soda lime glass (SLG) substrate and then selenized at 550℃ for 40minutes, exhibited a single chalcopyrite phase, uniform and dense morphology, and columnar grains. It is also found that the optical band gaps of the films are in the range of 1.21~1.24eV.