Abstract: At present, the three-roll cross-rolled perforated large-sized thin-walled magnesium alloy tubes are prone to form tail triangles.Therefore, a method of large-size AZ31 magnesium alloy thin-walled seamless pipes produced with a billet diameter of 110 mm by using two cone rolls was proposed.The principle of two-roll and three-roll cross-rolling piercing was analyzed. According to the characteristics of magnesium alloy materials, the corresponding deformation process parameters were formulated, and the whole process was numerically simulated by Deform-3D finite element software. The results of equivalent strain, rolling speed, and equivalent stress were analyzed. The simulation results show that the tube shape is uniform and the tail section is round.