The emergency department in a hospital, as its name implies, is a facility to be utilized by those who require emergency medical care. This paper introduces the longitudinal organization of the patient handling called "emergency path" and it discusses the application of the company modelling methods especially the GRAI methodology in the emergency department. The goal is to optimize these paths and to improve the quality of the patient handling while mastering the costs. The development of this model was based on the ED and three geriatrics, neurology and traumatology services. Simulation was used in this paper to assess the effects of some changes at the ED of the Medical Center of Valenciennes in France. Our survey is integrated into the regional project whose theme are the emergency paths that have just been created at the ED of Valenciennes Hospital center and will contribute to the ED service project achievement.