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An optimization problem is formulated to obtain the desired shape of a forming product.The results of a forming process depend on the shape parameters of the blank shape.Structural optimization has been applied to obtain the desired shape of sheet forming.The equivalent static loads method for non linear static response structural optimization (ESLSO) has been utilized to perform sheet forming optimization since nonlinear dynamic analysis is required in sheet metal forming analysis.In the method, equivalent static loads (ESLs) are defined based on the strains.Strain ESLs are static loads that generate the same displacement as well as strain fields of linear static analysis as those of nonlinear dynamic analysis.In this paper, a new method for stress ESLs is presented using a similar concept of the method to calculate strain ESLs by redefining the value of material properties.That is, ESLs that generate the same displacement as well as stress fields of linear static analysis as those of nonlinear dynamic analysis and the generated ESLs are used in the optimization process.A cup sheet metal forming optimization problem is performed to obtain the desired shape using the stress ESLs.The forming process is analyzed by using the finite element method a commercial system called LS-DYNA is used for the analysis.Nastran is used for optimization.