The　as-cast　microstructure　of　Fe-4Cr-B　alloy　has　been　systematically　investigated,　which　contains　1　wt%B,　4　wt%Cr,　0.35　wt%C,　0.8　wt%Si　and　0.8　wt%Mn.　The　investigation　was　carried　out　by　optical　microscopy　(OM),　scanning　electron　microscopy　(EDS/SEM),　X-ray　diffraction　(XRD),　hardness　tester　and　wear　tester,　and　the　quenching　temperature　effect　on　its　microstructure　and　mechanical　property　was　studied.　The　results　showed　that　ferrite,　pearlite,　martensite　and　borocarbides　were　the　main　composition　of　the　solidification　microstructure　of　casting　Fe-4Cr-B　alloy.　After　water　quenching　at　950-1150　degrees　C,　the　matrix　transformed　to　martensite,　and　the　secondary　borocarbides　M-23　(C,　B)(6)　precipitated　from　the　matrix,　and　then　the　continuous　distribution　of　M-2　(B,　C)　(M　=　Fe,　Cr,　Mn)　among　dendrites　began　to　break.　As　the　water　quenching　temperature　increased,　the　phenomenon　of　disconnection　became　more　clearly.　When　the　water　quenching　temperature　was　1100　degrees　C,　the　network　borocarbides　fractured　and　formed　an　isolated　distribution.　The　hardness　of　the　alloy　increased　first　and　then　decreased.　At　water　quenching　temperature　of　1100　degrees　C,　the　hardness　reached　the　maximum　of　62.8　HRC.　The　abrasive　resistance　and　hardness　of　casting　Fe-4Cr-B　alloy　changed　at　the　same　trend.