This work presents a study of the System Dynamic as a support tool for decisions of the project leadership, demonstrating its use and application in a large-scale technology implementation project. Its objective is to make possible for the project management to have an analysis tool that provides the anticipation of the projects existent interferences, such as the need of additional resources, project decisions failures, scope changes, requests for additional activities not directly related to the project. The dynamic analysis requires the manipulation of many variables and needs a tool that supports the project leadership in their vision and better understanding of the overall project. With the proposed technique, project leadership, decision makers and managers in general can analyze the variables of a process and their dependencies. First, the work describes the theory related to System Dynamic, presenting a brief technique history and conceptual information. After that, it explains about Enterprise Resource Planning (ERP) implementation projects, their main characteristics, conceptual models, phases, main products and the required organizational structure. Afterwards, it introduces the main project management hard (formal) and soft (causal) models, applying the system dynamic based on the ERP implementation concepts and demonstrating the existing influences.