In order to solve the problem of difficult processing about magnesium alloy seamless tube, the process prepared by rotary piercing technology for AZ31 magnesium alloy pipe was studied in the paper. According to the constitutive relation of magnesium alloy during hot working, temperature and strain rate range of 300 ℃-450℃, 0.001 s-1 - 1s-1 were confirmed. According to the theory of skew rolling and the existing three-roll skew rolling equipment, the process parameters were preliminary determined. The coupled thermal-mechanical numerical simulation and experiment research of the AZ31B magnesium alloy billet with the size of Φ40mm×300mm were carried, taking samples after rolling for metallographic analysis.The results showed that the rotary piercing way could produce AZ31 magnesium alloy seamless tube; At 400 ℃, choosing appropriate amount of plug advance、feed angle、roll speed, and piercing gorge diameter would be able to pierce Φ40mm×5.5mm×615mm magnesium alloy tube; After piercing microstructure changed into equiaxed distribution and grains were refined to 3 microns, mechanical performance was improved accordingly. This process could be instead of traditional magnesium alloy extrusion process to produce seamless tube, improving production efficiency, reducing costs, which facilitated subsequent product production.