A finite element analysis was conducted on the plastic deformation of 6 mm AZ31 magnesium alloy thin plates rolled asynchronously. Different reduction rates were adopted to analyze their influences on the bending deformation, rolling force, equivalent stress, and equivalent strain of the plates. The finite element analysis of asynchronous rolling was carried out when the single-pass reduction rates were 66%, 58.3%, 51.6%, 41.6%, and 35%, respectively. The results show that as the reduction rate decreases, the rolling force increases. Furthermore, considering the influencing factors of the rolling process parameters, it is determined that when the optimal rolling process reduction rate is 41.6%, the rolling effects of rolling force, stress, and strain are better, which is conducive to the rolling process.