High quality magnesium alloy sheets with non-dendritic microstructure can be manufactured by the technique which incorporates semi-solid processing with continuous roll stripcasting. In particular, the process is believed to be cost-effective in mass production of magnesium sheet products. The processing parameters, such as roll speed and temperature, have significant influence on roll strip-casting process. In this paper, the commercial software, DEFORM-3D, for deformation simulation of bulk materials was used to carry out the simulation of roll strip-casting process for AZ91D magnesium alloy in semi-solid state, and the distribution of equivalent stress, equivalent strain and temperature was obtained. Based on the results, the optimization of processing parameters was discussed.