The　effect　of　austenitizing　temperatures　at　850,　880,　910,　940,　970　and　1000　degrees　C,　respectively,　and　tempering　at　250　degrees　C　on　the　microstructure,　mechanical　properties,　strengthening　and　toughening　mechanism,　and　wear　behavior　of　Si-Mn-Mo　cast　steel　containing　0.45%C-2.0%Si-1.0%Mn-0.3%Mo-0.8%Cr-0.004%B　were　systematically　investigated.　The　results　indicated　that　the　microstructure　of　water　quenching　Si-Mn-Mo　cast　steel　was　mainly　composed　of　lenticular　martensite,　martensite/austenite,　bainitic　ferrite　and　retained　austenite.　After　tempering,　the　homogeneity　of　the　microstructure　improved.　As　the　austenitizing　temperature　increased,　the　hardness　of　the　steel　increased　first,　and　then　it　remained　almost　constant,　the　impact　toughness　decreased　significantly,　and　the　wear　loss　decreased　first　and　then　increased.　Under　low　wear　load,　the　steel　austenitizing　at　910　degrees　C　had　excellent　wear　resistance　before　and　after　tempering.　Under　high　wear　load,　after　tempering,　the　steel　austenitizing　at　850　degrees　C　had　the　optimum　wear　resistance.　The　wear　mechanisms　were　mainly　abrasive　wear,　oxidation　wear　and　adhesive　wear.