The stringers support various loads such as aerodynamic force and tare weight acting on the main wings of the airplane to prevent buckling of the skin. Using a combination of mechanical and forming process, the process of the stringer minimizes the residual stresses in the stringer and shortens the process time. A forming press is a forming machine that uses a press to bend a stringer manufactured by mechanical process. The conventional forming press actuates the press head with oil-hydraulic actuators, making precise control difficult. In addition, since a separate oil-hydraulic pump is required to generate the hydraulic pressure, the space utilization is low and the working environment may deteriorate due to oil leak. By changing the power source of the forming press to a servo-motor, the press head can be controlled precisely, and thus it is possible to produce high quality products, and it is possible to make the equipment smaller and lighter because there is no need for additional device such as oil-hydraulic pump. However, in order to develop the forming press of the servo-motor type, it is necessary to carry out a structural examination on various design factors because the design modification of main structures in the forming press should be made. Therefore, this paper is to carry out a design review for a press block that is subjected to a direct load when a forming press process a stringers. First, we define the radius of curvature of the side and the fillet radius of the edge in contact with the stringer with the design variables of the press block and then examine the structural stability through the nonlinear structure analysis and derive the optimal shape. Second, we predict the plasticity change of the stringer according to the stroke displacement of the press head by performing the plasticity analysis based on the optimal shape derived from the structural analysis. Based on the results of this study derived through this process, it is expected that the structural stability of the forming press can be secured and a database necessary for the control algorithm can be secured.