A new approach for the CPA treatment of band structure of semiconductor alloys based on the LMTO-ASA-VCA method is suggested, in which no adjustable parameter is needed. In. order to construct a set of orthonormal sp-like hybrid orbitals from calcutated eigenstates and apply for CPA calculation, it is found that the following procedure is suitable: in the process of LMTO calculation and its VCA treatment, d states of atoms should be included in the matrix elememts, and d-band hybridization effect may be regarded as negligible for the secu-ler equation calculation. This method is illustrated with GaAlAs alloys. The results indicate that the CPA's calculation values of bowing parameters of bands and band-edges are quite reasonable.