In recent years the progress in computational mechanics has made it possible to adopt more sophisticated constitutive models for solving complicated plasticity problems. For the formulation of elastic-plastic theory at finite strain, E.H. Lee decomposed the deformation gradient into a product of the elastic and plastic parts instead of assuming that the strain rate is the combination of the elastic and plastic strain rates. A finite element model has been formulated based on E.H. Lee's theory. Accordingly, a three-dimensional general purpose finite element software package has been developed. The simple tension problem and the simple shear problem are solved as examples so that the numerical solutions and the exact analytical solutions can be compared. Finally, a tensile test of a thin-walled aluminum alloy tube is solved and compared with the experimental data. The good agreement between the finite element solution and the experimental data demonstrates the validity and applicability of the proposed numerical model.