Abstract: To fullfill the demand of rolling accuracy of magnesium alloy sheets， the symmetric problem during rolling process and the microstructural evolution of the AZ31 sheets with the thickness of 0.5 and 1.0mm， which made by symmetric and asymmetric rolling process using small rollers， were investigated. The results showed that the average grain size in the 0.5mm sheets by symmetric and asymmetric rolling was 10.1 and 8.8μm， respectively， that of the 1.0mm was 16.7 and 13.6μm， respectively. The element equivalent strain of the 0.5mm sheet was up to 0.42 by asymmetric rolling and 0.29 by symmetric rolling and that of the 1.0mm was 0.75 and 0.66， respectively. In symmetric rolling， the distributions of the nodal equivalent Mises stress and shear stress in the 0.5mm sheet were more symmetric by symmetric rolling process， in contrast with those by asymmetric rolling. Grain growth in the 0.5mm sheet by asymmetric rolling was much slower than that by symmetric rolling during annealing for 1h at 250， 300 and 350℃. At 350℃， the average grain size in the 0.5mm sheet by asymmetric rolling was 9.8μm and that by symmetric rolling was 24.9μm.

Key words: asymmetric rolling, symmetric rolling, simulation, annealing