In　this　article,　the　effect　of　boron　concentration　(B　=　0,　0.4,　0.8,　1.4　and　2.0　respectively)　on　the　solidification　microstructure　and　properties　of　Fe-Cr-B　alloy　containing　0.35%　C,　10-12%　Cr,　0.5-0.8%　Si,　and　0.7-1.0%　Mn　was　studied　by　means　of　the　optical　microscope　(OM),　the　scanning　electron　microscope　(SEM),　X-ray　diffraction　(XRD),　Rockwell　hardness　and　Vickers　hardness　tester.　The　results　indicate　that　the　microstructure　of　boron-free　sample　consists　of　the　martensite,　and　its　hardness　reaches　59.2　HRC.　When　a　small　amount　of　boron　element　was　added,　the　eutectic　phase　of　network　structure　generated　along　the　grain　boundary.　The　amount　of　eutectic　phase　increases　when　the　boron　concentration　increases.　Moreover,　the　eutectic　phase　is　the　mixture　of　boride　and　boron　carbide.　The　boride　is　Fe(2)B　and　the　boron　carbide　is　(Cr,　Fe)(7)(C,　B)(3).　Compared　with　boron-free　sample,　the　Rockwell　hardness　of　the　samples　with　different　boron　concentrations　are　all　higher,　above　62　HRC,　and　the　hardness　grow　up　with　the　increase　of　boron　concentration.　When　the　boron　concentration　reaches　to　1.4%,　the　Rockwell　hardness　of　the　alloy　is　65.7　HRC,　which　is　the　highest　in　this　study.　When　the　boron　concentration　rises　to　2.0%,　the　hardness　has　no　obvious　change.