By considering the coupled thermo -mechanical relations between temperature and deforming,a numerical sim ulation of the special long forging for 1420Al -Li alloy dur ing inverted extrusion was done by using rigid visco-plastic finite elem ent method in this paper.The relations between total load and the displacement,the distribution of s tress,strain,temperature and stra in rates during forging,which can provide useful information for the p rocess design,were gained.