To understand more about the rolling process of an AZ31 magnesium alloy sheet and the difference of simulation results between 2D and 3D, the rolling experiment of AZ31 was carried out and some useful data were obtained, and then the rolling processes were simulated by DEFORM2D and 3D respectively. The simulation results are in good agreement with the experimental results based on selecting the correct parameters of stress-strain relationship of AZ31, the friction factor with or without lubricant and the interfacial heat transfer coefficient. The influences of rolling reduction, workpiece temperature and roller temperature on the rolling load and torque are discussed and the difference of simulation results between 2D and 3D is illustrated.