This thesis studies the change in the Moroccan hospitals and contributes in the field of change management. The result of our research is a new method of change management. This method represents the proposed change through the perceptions of those involved in this change, incorporating it into a strategic planning. This is the Actors' Representations of Change method which is based on a teamwork and a modeling of internal and external factors influencing the hospital change. Indeed, the hospital organization has certain characteristics tightly linked with the question of change management. Its structure emphasizes the operational centre and the importance of the actors. A change management that takes into account the actors is very linked to its context as it aims to involve and engage the actors in its finality. Our objective is to conceive a representation of the actors' perceptions to succeed in the changes led by the Hospital Establishment Project. To reach this objective, we adopt an Engineerical Methodology of Research (Chanal and al., 1997) which justifies our multidisciplinary position and helps us to collaborate closely with the hospital actors.