To get ready for the hard international competition, firms have to convince themselves of the pressing necessity of optimizing its competitiveness factors. In this perspective, this article proposes a general model of management system of firms through the implementation of tools of Lean Manu-facturing. This method establishes an approach to introduce an action plan to improve the perfor-mance of a firm. Knowing that the Algerian firms do not escape the constraints of competitiveness, the adopted model is applied to two strategic firms of the Algerian industry and the final result gives a series of measures to improve their competitiveness and their performances, simultaneously.