In this paper, multi-stage optimum design of composite pressure vessels is presented. The design variables for composite vessels include the head shape, the winding angle, the layer thickness, the number of layers, and the stacking sequence. A parameter called modified shape factor is introduced as an objective function. This parameter takes into account the effects of the internal pressure and volume, the vessel weight, and the composite material properties. The proposed algorithm uses genetic algorithm and finite element analysis to optimize the design parameters. As a few examples, this procedure is implemented on geodesic and ellipsoidal heads. The results show that for the given vessel conditions, the geodesic head shape with helical winding angle of nine degrees has the better performance.