The　microstructures,　mechanical　properties　and　abrasive　wear　behaviour　of　five　kinds　of　Si-Mn-Cr-B　cast　steels　were　studied.　The　steels　investigated　contained　X　wt.%　C　with　X=　0.15,　0.25,　0.35,　0.45,　0.55,　2.5　wt.%　Si,　2.5　wt.%　Mn,　0.5　wt.%　Cr,　0.004　wt.%B.　The　results　showed　that　the　A(c1)　temperatures　increased　and　A(C3)　and　M-s　temperatures　decreased　with　increasing　carbon　concentration.　From　the　continuous　cooling　transformation　(CCT)　curves,　it　was　discovered　that　the　incubation　period　of　pearlitic　transformation　was　prolonged　and　the　transformation　curves　of　pearlite　and　bainite　were　separated　significantly　with　rising　carbon　concentration.　At　lower　carbon　concentration,　the　normalized　structure　of　Si-Mn-Cr-B　cast　steel　consisted　mainly　of　granular　banite　and　M-A　islands.　The　normalized　microstructures　of　the　cast　steel　changed　from　granular　bainite　gradually　to　needle-like　bainite,　upper　bainite,　and　lower　bainite　with　rising　carbon　concentration.　The　tensile　strength　and　hardness　of　Si-Mn-Cr-B　cast　steel　increased　and　impact　and　fracture　toughness　decreased　with　increasing　carbon　content.　The　wear　testing　results　showed　that　the　wear　resistance　of　Si-Mn-Cr-B　cast　steel　improved　with　higher　carbon　content　but　was　obviously　unchanged　beyond　the　carbon　concentration　of　0.45%.　The　best　balance　of　properties　of　Si-Mn-Cr-B　cast　steel　is　obtained　at　the　carbon　concentration　range　of　0.35-0.45%C.