Phase transformations which lead to dramatical property change are very important for engineering materials. Phase-field methods are one of the most successful and practical methods for modelling phase transformations in materials. The Cahn-Hillard phase-field model is among the most promising phase-field models. The most successful aspect of the model is that it can predict spinodal decomposition (which is essential to determining the microstructure of an alloy) in a binary system. It is used in both materials science and many other fields, such as polymer science, astrophysics, and computer science. In this study, the Cahn-Hillard phase-field model is evaluated by an analytical approach using the (1/G )-expansion method. The solutions obtained are tested for certain thermodynamic conditions, and their accuracy of predicting the spidonal decomposition of a binary system is confirmed.