Using　WB　powder　and　WC-Co　powder　as　raw　materials,　the　cemented　carbides　with　different　volume　fractions　of　WB　additives　were　prepared　by　a　hot　isostatic　pressing　(HIP)　method.　Then,　the　phase　constitution,　microstructure　and　mechanical　properties　of　the　prepared　cemented　carbides　have　been　studied.　The　results　show　that　the　super　hard　WCoB　phase　is　formed　by　the　reaction　of　WB　and　Co.　With　the　decrease　of　Co　phase,　less　WC　grains　are　separated,　and　thus　the　toughness　is　decreased.　With　the　increase　of　the　WB　addition,　the　prepared　cemented　carbides　have　lower　friction　coefficients　and　better　wear　resistance　and　hardness.　When　the　WB　addition　is　30wt%,　the　hardness　of　19　000　MPa　can　be　attained.　The　abrasion　loss　of　the　sample　is　1/10　of　that　of　the　WC-Co　cemented　carbide.　However,　the　fracture　toughness　of　the　cemented　carbide　with　WB　addition　is　about　83%similar　to　91%　of　that　of　the　conventional　WC-Co　cemented　carbides.