Abstract: The Mg-5Sn-Si-0.9Sb magnesium alloy was subjected to multi-pass unidirectional rolling with rolling temperature of 370 ℃and rolling reduction of 10%. After rolling, the alloy was treated with solid solution +aging. The microstructure and properties of hot rolled and heat treated Mg-5Sn-Si-0.9Sb magnesium alloys were investigated.The results show that with the increase of pass, the second phase content of the rolled alloy increases and the size decreases, and the polygon tip angle of the primary Mg₂Si phase is gradually passivated and broken into a spherical polygon. The Mg₃Sb₂ phase and Mg₂Si phase are found in the microstructure of the alloy, and the Sb inhibits Mg₂Si phase growth.A new Sb-Mg₂ (Si_xSn_1-x)phase is formed after rolling.The complete dynamic recrystallization occurs after 4 passes of rolling, and the grain is refined, which is 15-20 μm.The tensile strength and elongation of the as-cast alloy are 106.1 MPa and 7.8%respectively.After rolling and T6 heat treatment, the material properties are significantly improved, and the tensile strength and the elongation after breaking of the alloy are increased to 213.8 MPa and 11.6%respectively.