The effect of misch metal and silicium additions to AZ31 magnesium alloy on the microstructure was investigated in this study. The results showed that needle shape Al11RE3 phase and polygonal type Mg2Si phase formed when misch metal and silicium were added to AZ31 magnesium alloy, which providing refined microstructure compared to AZ31 magnesium alloy. The coarse Chinese script type Mg2Si phase is not found. In addition, the β-Mg17Al12 phase completely divorced and formed many white particle phase. Based on the present experiment , the optimal additions of RE and Si were 0.5 wt% and 0.4 wt%, respectively.