Abstract: Now a days, business IT alignment requires the implementation of a powerful alignment model allowing a perfect coherence of all the actions and the decisions with the strategic objectives of the company which must be declined in an operational way with the business processes in order to align them with the information system. This study proposes an approach for the management of the evolution business IT alignment through the analysis of the gaps between the models of alignment As-Is and To-Be. This gap analysis is based on a set of metrics that make it possible to study the existing links and calculate the differences between the different layers of the enterprise architecture. Also this research has been validated through a case study of a real project in a Moroccan public administration.