Using magnetron sputtering technology, the CuInSi nanocomposite thin films were prepared by magnetron co-sputtering method and multilayer synthesized method respectively,and followed by annealing in N2 atmosphere at different temperatures. The structure of CuInSi nanocomposite films were detected by X-ray diffraction (XRD); X-ray diffraction studies of the annealed films indicate the presence of CuInSi, the peak of main crystal phase is at about 2θ=42.308°,meanwhile,there are In2O3 peak and other peaks in the XRD patterns of films. The morphology of the film surface was studied by SEM. The SEM images show that the crystalline of the film prepared by multilayer synthesized method was granulated, But the crystalline of the film prepared by magnetron co-sputtering with needle shape. The grain size is a few hundred angstroms. The band gap has been estimated from the optical absorption studies and found to be about 1.40 eV for the sample by magnetron co-sputtering, and 1.45eV for the sample by multilayer synthesized, but all changes with the purity of CuInSi.