In order to investigate the flux uniformity of melt at the outlet of T die,the melt flow and die deformation in a T die are analyzed by a coupling numerical simulation with CFD software Polyflow.The results show that the deformation of the flow channel surface along mold thickness nonlinearly varies in the extrusion direction and the die width direction,which results in great discrepancy between the simulated melt flux uniformity at the outlet and the theoretical one without considering die deformation.Moreover,it is pointed out that,with the increase of extrusion output,the slit deformation along the mold thickness increases and the melt flux uniformity at the oulet decreases,and that opposite results can be obtained when the die thickness increases.