To predict and improve formability of tube bending process for copper JIS25A material, geometric parameters of bending process were considered according to Taguchi's orthogonal array then coupled with the finite element method (FEM) simulations. First, the stress-strain curve of material was input into ABAQUS/Explicit finite element code to predict the initial results of tube bending process. Three parameters variable - the diameter of ring mandrel, distance of two rings, distance of mandrel and base were then selected to establish their effects on the quality of bending process. The optimum simulation case was finally confirmed by corresponding experiment.