It is shown that by means of the solutions obtained by the random phase approximation, the generalized configuration mixing (GCM) method can provide better approximate solutions in a rather simple and systematic way. A set of explicit expressions for the matrixelements involved in the eigenvalue equation of the GCM method has been derived. Further, it is proved that the GCM method is self-consistent, and the equation of motion satisfied by the corresponding Green function and its series expansion have been obtained. By means of the latter, the property of the eigensolution determined by the GCM method is discussed.