Abstract: The SM master alloy was used to add high oxygen affinity elements Mn and Si into the sintered steel as alloying elements to improve the mechanical properties. The results show that the ultimate strength of sintered steel with 1.1%-1.7%Si,2.7%Mn and 0.35%C is above 800MPa. But the addition of SM master alloy has some deleterious effect on the toughness of sintered steel. By comparing the SM master alloys with two different compositions,the effect of SM master alloy with high content of Si and Mn is more remarkable.