This work entitled - Elastoplastic Analysis of a Metallic Mast with Stiffeners - is devoted to optimize the weight of masts. These masts are made of steel and have a conical geometry with constant thickness. The masts are considered clamped at their lower basis in soil. The masts should resist to the applied loads which are self weight, wind and equipments. Firstly, two types of design have been proposed to pursue this study; Type A consists of adding longitudinal stiffeners and type B consists of changing the whole shape of the masts section. Deflection tests will be applied to the type A of masts according to the metallic standards, these same tests will be applied also on normal masts. The test results will be analyzed to study the effects of the stiffeners on the mechanical behavior of the masts. Many computational cycles are realized by a numerical software to prove that we have the same results on the type A masts either by experimental tests or numerical simulation, hence, we will analyze the mechanical behavior of type B by using only the mumerical simulation method. The results have shown that both type A and type B allow a considerable weight optimization. Finally, an analysis of the two solutions proposed will be done in order to determine the advantages and disadvantages of each one of them.