The simulation rolling and actual rolling of AZ31 strip with a thickness of 3mm prepared by a vertical twin roll caster (Ø250×150mm) have been made by both Gleeble-1500D thermal simulation testing machine and Ø170×300mm rolling-mill. The influence of various rolling parameters such as temperature (250°C, 300°C, 350°C and 400°C) and reduction (40%, 50% and 60%) on the microstructure of the rolled AZ31B thin strip have been investigated by means of metallographic observation and grain size measurment. The results indicate that when the temperature increases, the grain size of the rolled strip increases and the uniformity decreases. When the reduction is 50% the grain size is 10~30μm and the grains are fine and uniform. When the reduction is 40% or 60%, the grain size is 5~180μm and the grains are coarse in some areas. An optimized rolling process, 350°C×50% is suggested for actual rolling and a uniform microstructure of rolled AZ31 strip is obtained.