The　microstructure,　mechanical　properties　and　wear　resistance　of　medium　carbon　alloy　steel　have　been　investigated　by　means　of　the　optical　microscope,　the　scanning　electron　microscope,　the　tensile　test,　the　hardness　test,　the　impact　test,　the　fracture　test　and　the　wear　test.　The　results　show　that　the　bainite　and　retained　austenite　were　obtained　under　the　condition　of　air　hardening　in　the　carbon　steel　containing　0.30-0.45　wt-%C,　by　increasing　the　concentrations　of　silicon　and　manganese,　adding　proper　boron,　nickel,　vanadium,　titanium　and　rare　earth,　and　appending　the　pretreatment　of　pearlitic　anneal.　The　hardness,　tensile　strength,　impact　and　fracture　toughness　of　bainitic　steel　excelled　50　HRC,　1800　MPa,　30　J　cm(-2)　and　70　MPa　m(1/2)　respectively.　It　had　excellent　wear　resistance　under　the　two-body　pin　on　disc　wear　and　three-body　impact　wear.　The　serving　period　of　hammer　made　of　bainitic　cast　steel　is　1.5-2.0　times　longer　than　that　of　Hadfield　austenitic　steel.