Abstract: The aim of the present work is to study the reduction of multi-parameter singular perturbation bilinear systems. Because the model obtained via the singular perturbation method is not bilinear in general, further approximation is developed, yielding a reduced order model. No details about small parameter are needed in the study, thus the difficulties of complex computation are avioded due to the simplicity of this approach. The validity of the proposed method is demonstrated by its application to bilinear models of an ammonia reactor and methanol reactor, the later of which is established in this paper.