The mechanical properties,chemical properties and biocompatibility of Mg-3Sn—0.5Mn alloy were tested.A series of in vitro evaluations such as tensile test,static and dynamic immersion test,hemocompatibility test as well as cytotoxicity test were presented,with commercial magnesium alloy WE43 as the control.Mg-3Sn-0.5Mn alloy possesses suitable strength and superior ductility compared with WE43 and AZ31.Static immersion and dynamic degradation tests showed more uniform degradation with a more moderate rate for Mg—3Sn—0.5Mn alloy(0.34 mm/y in static condition and 0.25 mm/y in dynamic condition)compared with WE43 alloy(0.42 mm/y in static condition and 0.33 mm/y in dynamic condition) in Hank’s solution.Blood compatibility evaluation suggested that Mg—3Sn—0.5Mn alloy had no destructive effect on erythrocyte and showed excellent anti-thrombogenicity to blood system.Besides,Mg—3Sn—0.5Mn alloy showed no inhibition effect to L929 metabolic activity and mild toxicity to vascular smooth muscle cell(VSMC) in preliminary cell viability assessment.By considering its excellent mechanical strength,corrosion resistance,low ion release rate and good biocompatibility,Mg—3Sn—0.5Mn alloy may be a promising economical candidate as biomedical implant material for load-bearing clinical applications in the future. The mechanical properties, chemical properties and biocompatibility of Mg-3Sn-0.5Mn alloys were tested. A series of in vitro evaluations such as tensile test, static and dynamic immersion test, hemocompatibility test as well as cytotoxicity test were presented, with commercial magnesium alloy WE43 as the control. Mg-3Sn-0.5Mn alloy possesses suitable strength and superior ductility compared with WE43 and AZ31. Static immersion and dynamic degradation tests showed more uniform degradation with a more moderate rate for Mg-3Sn-0.5Mn alloy (0.34 mm / y in static condition and 0.25 mm / y in dynamic condition) compared with WE43 alloy (0.42 mm / y in static condition and 0.33 mm / y in dynamic condition) in Hank’s solution. Blood compatibility evaluation suggested that Mg-3Sn-0.5Mn alloy had no destructive effect on erythrocyte and showed excellent anti-thrombogenicity to blood system.Besides, Mg-3Sn-0.5Mn alloy showed no inhibition effect to L929 metabolic activity and mild toxicity to vascular s mooth muscle cell (VSMC) in preliminary cell viability assessment. By considering its excellent mechanical strength, corrosion resistance, low ion release rate and good biocompatibility, Mg-3Sn-0.5Mn alloy may be a promising candidate for biomedical implant material for load- bearing clinical applications in the future.