In this paper a new model has been proposed to describe the oxidation of Si-Al-O-N materials in both isothermal and non-isothermal conditions in the form of powders and pellets. All these formulae are analytic with a form of explicit function; therefore, they are not only easy to use but also enable the easy performance of a theoretical analysis. The application of these formulae to practical systems shows that this model is feasible; moreover, these formulae can not only be used to treat the oxidation for Si-Al-O-N materials but also be applied to treat reactions in other fields of materials.