The FE simulation process of cold extrusion forming internal threads with advanced non-linear FEA software ANSYS/LS-DYNA by using FEA method of rigid-plastic is achieved. Then the distribution law of stress and strain in cold extrusion forming are obtained

and the FEA method of metal plastic forming is described in detail. The result indicates that compression strain on external surface and tensile strain on internal surface of the work piece are produced by tapping torque in cold extrusion process

and strain increases gradually from inside surface to outside surface

the maximal strain appeares on outermost surface

the tensile strength and fatigue property of internal threads are greatly improved

which playes a guideline role for controlling technical parameters in cold extrusion process of internal threads and simulation of FEA method in plastic forming.