With the increasing of competition in all industrial sectors, the supply chain management is more and more considered as playing an essential role as far as the company's improvement is concerned. Depending on the cases, different approaches can be used for this research of global optimization, such as simulation or business process re engineering techniques. This paper aims at proposing a methodology combining these two approaches in order to establish a diagnosis of a business process in a supply chain context. We will first focus on the simulation contribution to supply chain optimization. Then, the paper will go on to suggest a methodology which will lead to the identification of the business process. Finally, we will present its application to the order fulfillment business process of an industrial case, using Aris and Arena Softwares, before discussing the benefits of simulation for the quantification of malfunctioning, the identification of new ones and the evaluation of solution.