The thixoforming of wrought magnesium alloy was analyzed with computer numerical simulation based on rigid plastic/rigid viscoplastic finite element method. The simulated parameters were chosen and depended on the constitutive model of semi-solid AZ61 alloy that was established using the multiple nonlinear regression method in our prior literature. Thixo mechanical properties of semi-solid AZ61 alloy in high solid volume fraction were also analyzed. Behaviors of metal flow and temperature field were obtained, which were also compared with experimental data in literature. Research showed that the hard deformation magnesium alloy had great filling ability in semi-solid state, and the stress and strain distributions in workpiece after thixoforming were uniform. The semi-solid thixoforming technology has taken priority of the traditional processing.