The rolling speed is the key process parameter in the three-roll cold rolling forming process, which determines its mechanical characteristics and temperature rise. Based on this phenomenon, this paper takes cold-rolled AZ31 magnesium alloy tubes as the research object, by numerical simulation, compares and analyzes the influence of different rolling speeds on the equivalent stress, equivalent plastic strain and joint temperature of each characteristic deformation section. The results show that these parameters increased with the increase of rolling speed. By means of the cellular automaton model and experiment, the preliminary evolution law of continuous recrystallization and refinement of the grain during the rolling process was proved. The comparative analysis experiment and simulation results were combined with various factors to obtain 800mm/s. The rolling speed can better meet the requirements of the process requirements, which provides a basis for the selection of rolling speed of cold-rolled magnesium alloy tubes.