Aluminum-doped Ge(2)Sb(2)Te(5) (Al(x)GST) films were deposited on Si(100) substrates by co-magnetron sputtering system. The Aluminum concentrations in these films are determined by X-ray photoelectron spectroscopy (XPS). The influence of Al doping upon phase change characteristics of these Al(x)GST alloy films has been investigated by X-ray diffraction (XRD) and a temperature-regulable UVISEL(TM) typed spectroscopic ellipsometry (TRSE). With the augment of Al doping concentration, the crystalline temperatures of Al(x)GST films went up while annealing, and the face-centered-cubic (fcc) phase had high thermal stability. The reflectivity contrast of the films increases obviously, which is effective to improve the signal to noise ratio (SNR) for optical phase-change storage.