On the basis of their similarities with forward rod extrusion, three analytical force computation models are introduced for the forming force prediction of sheet metal extrusion. By comparing with finite element solutions, it has been found that the forming forces obtained by these models deviate at more or less 30% from the numerical solutions under different area reductions. These deviations are due to the neglect of friction or shear force terms in the models. Therefore, a new model, one that fully considers the contributions of extrusion force, shear force, and friction terms to the forming force, is proposed. With tremendous numerical computations, the relationships between forming force and area reduction, sheet metal thickness, and penetration depth, among others are analyzed. Thereafter, the factors in the proposed model are determined. Additionally, a corresponding experiment work has been designed to validate the proposed model. Compared with the experimental results, the predicted results show a relative error of less than 15% under different extrusion ratios, which is acceptable in the industry.