Microstructure　of　the　medium　carbon　high-chromium　cast　iron　containing　boron　as-cast　and　tempered　at　different　temperatures　was　observed　by　optical　microscopy　(OM),　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD).　Hardness　of　the　cast　iron　was　measured　by　Rockwell　hardness　and　Vickers　hardness　tests.　The　effects　of　tempering　processes　on　the　microstructure　and　hardness　of　the　cast　iron　containg　boron　were　examined.　The　results　indicate　that　the　as-cast　microstructure　consists　of　austenite,　martensite　and　M7C3　(M=Fe,　Cr)　carbide.　After　tempering,　the　amount　of　austenite　in　the　matrix　decreases,　and　secondary　carbides　are　precipitated　and　the　austenite　transforms　into　martensite.　Rockwell　hardness　and　Vickers　hardness　are　57.4　HRC　and　596.7　HV,　respectively,　for　the　cast　iron　after　double　tempering　at　530°C　and　500°C.　Based　on　the　experiment,　the　double　tampering　process　is　recommeded,　which　is　tempered　at　530°C　for　the　first　and　then　at　500°C　for　the　second.