The microstructure evolution and mechanical properties of biodegradable Mg–3Sn–1Zn–0.5Mn alloys were investigated by the optical microscopy, X-ray diffractometer and a universal material testing machine.The corrosion and degradation behaviors were studied by potentiodynamic polarization method and immersion test in a simulated body fluid(SBF). It was found that the as-extruded Mg–3Sn–1Zn–0.5Mn alloy has the fine equiaxed grains which underwent complete dynamic recrystallization during the hot extrusion process, with the second phase particles of Mg_2Sn precipitated on the grain boundaries and inside the grains. The tensile strength and elongation of as-extruded Mg–3Sn–1Zn–0.5Mn alloys were 244 ± 3.7 MPa and 19.3% ± 1.7%, respectively. The potentiodynamic polarization curves in SBF solution indicated the better corrosion resistance of the as-extruded Mg–3Sn–1Zn–0.5Mn alloy in the SBF solution. Immersion test in the SBF solution for 720 h revealed that the corrosion rate of as-extruded Mg–3Sn–1Zn–0.5Mn alloy was nearly 4 ± 0.33 mm/year. The hemolysis rate of as-extruded Mg–3Sn–1Zn–0.5Mn alloy was lower than the safe value of 5% according to ISO 10993-4. As-extruded Mg–3Sn–1Zn–0.5Mn alloy showed good biocompatibility after being implanted into the dorsal muscle and the femoral shaft of the rabbit, and no abnormalities were found after short-term implantation. It was revealed that the as-extruded Mg–3Sn–1Zn–0.5Mn alloy is a promising material for biodegradable implants,which possesses an interesting combination of preferred mechanical properties, better corrosion resistance and biocompatibility. The microstructure evolution and mechanical properties of biodegradable Mg-3Sn-1Zn-0.5Mn alloys were investigated by the optical microscopy, X-ray diffractometer and a universal material testing machine. The corrosion and degradation behaviors were studied by potentiodynamic polarization method and immersion test in a simulated body fluid (SBF). It was found that the as-extruded Mg-3Sn-1Zn-0.5Mn alloy has the fine equiaxed grains which underwent complete dynamic recrystallization during the hot extrusion process, with the second phase particles of Mg_2Sn precipitated on the tensile strength and elongation of as-extruded Mg-3Sn-1Zn-0.5Mn alloys were 244 ± 3.7 MPa and 19.3% ± 1.7%, respectively. The potentiodynamic polarization curves in SBF solution indicated the better corrosion resistance of the as-extruded Mg-3Sn-1Zn-0.5Mn alloy in the SBF solution. Immersion test in the SBF solution for 720 h revealed that the corro The hemolysis rate of as-extruded Mg-3Sn-1Zn-0.5Mn alloy was lower than the safe value of 5% according to to ISO 10993-4. As-extruded Mg-3Sn-1Zn-0.5Mn alloy showed good biocompatibility after being implanted into the dorsal muscle and the femoral shaft of the rabbit, and no abnormalities were found after short-term implantation. It was revealed that the as-extruded Mg-3Sn-1Zn-0.5Mn alloy is a promising material for biodegradable implants, which possesses an interesting combination of preferred mechanical properties, better corrosion resistance and biocompatibility.