The crystal theory is formulated for treating the vibrational Green's functions of alloys. The configurations of the alloy could be symmetrized in virtue of the theory of permutation groups. The Hamiltonian of the alloy could be block diagonalized using the franslation group of the lattice, and completely diagonalized by applying Wilson's GF matrix method. So the inverse matrix of Green's functions is solved. Phonon's Hamiltonian and Green's func-tions are also mentioned.