Facing the increasing complexity of systems and their design methods, the Model Driven Engineering (MDE) brings solutions to facilitate and automate the software development process. The model transformation is the most important artifact in MDE that it defines the automatic passing from one model to another. The validation of such model transformation are necessary to improve the safety of this latter, but most transformation languages have not a formal semantics to add detailed specifications on the expected behavior. So it is important to give solutions to integrate formal methods at this level. For this, we utilize the Coq proof assistant that is based on various calculus, for validating a model transformation specified with QVT-operational language. We illustrate our approach by transforming a UML state diagram into Petri net.