The　microstructure,　mechanical　properties　and　abrasion　resistance　of　Fe-B　alloy　with　4wt%Cr-2wt%Mn-2wt%Cu　addition　have　been　systematically　investigated.　The　results　show　that　the　microstructures　mainly　consist　of　martensite　and　boride　(M2B)　in　the　as-cast　and　heat　treated　Fe-B　alloys;　after　heat　treatment,　the　morphology　and　volume　fraction　of　the　M2B　have　little　change,　meanwhile　the　nucleation　and　precipitation　of　secondary　borocarbide　M-23(C,　B)(6)　probably　take　place　in　an　in　situ　manner　within　martensite.　Moreover,　the　M2B　is　identified　as　chemical　formula　of　Fe2.04Cr0.11Mn0.07(B,　C)　reflecting　body-centred　tetragonal　(bct)　structure,　and　the　secondary　borocarbide　M23(B,　C)(6)　has　the　stoichiometry　of　Fe18.84Cr2.84Mn0.57(B,　C)(6)　with　face-centred　cubic　(fcc)　structure.　After　heat　treatment,　the　matrix　hardness　and　bulk　hardness　of　Fe-B　alloy　decrease　owing　to　the　decreasing　of　B/C　concentration　of　matrix　caused　by　the　precipitation　of　M-23(C,　B)(6),　while　the　fracture　toughness　of　Fe-B　alloy　increases.　Meanwhile,　the　heat　treatment　will　decrease　the　wear　resistance　of　Fe-B　alloy,　i.e.　the　wear　resistance　of　Fe-B　alloy　would　decrease　with　reduction　of　the　matrix　hardness.