he Al-6061-T6 tube’s drawing limit and the drawing process’s elasto-plastic behavior were investigated based on the foundational theories of larger deformation and continuum damage mechanics. A mathematical computation equation about the maximum Cockcroft-Latham damage value was converted to an appropriate discrete expression which is easy for FE code to programme, thus the corresponding finite element numerical algorithm for damage computation was developed. By an approach that physical experiments and numerical simulation provide mutual support for the critical damage value, the crack criterion of Al-6061-T6 was evaluated as 1.34. The crack criterion obtained was introduced as important design considerations of tube drawing process. An 3D graph which reflects maximum damage variation according with the diameters at different tube thickness was achieved, according to which the drawing process’s safe and unsafe areas of Al-6061-T6 tube with diameter 10mm at temperature 20°C and drawing velocity 100mm/s was ploted.