In　this　work,　the　microstructure,　the　formation　characteristics,　and　the　growth　mechanism　of　eutectic　borocarbide　during　solidification　in　high　boron　high　speed　steel　with　2.0　wt%　B-0.4　wt%　C-6.0　wt%　Cr-4.0　wt%　Mo-2.0%　Al-1.0　wt%　Si-1.0　wt%　V-0.5　wt%　Mn　are　investigated　utilizing　liquid　quenching　technology.　The　experimental　results　illustrate　that　the　as-cast　microstructure　of　high　boron　high　speed　steel　consists　of　alpha-Fe　matrix,　eutectic　borocarbide　M-2(B,C)　with　continuous　network　structure,　M-3(B,C)　boron-cementite,　and　M-7(C,B)(3)　(M　=　Fe,　Cr,　Mo,　V,　Mn).　Different　precipitating　sequences　of　eutectic　borocarbides　with　various　compositions　are　revealed.　During　solidification,　order　of　precipitation　is　Cr-rich　borocarbide　and　Mo-rich　borocarbide,　respectively.　Mo-rich　borocarbide　precipitates　from　the　existing　Cr-rich　borocarbide　rather　than　forming　independently.　Additionally,　the　growth　mechanism　of　different　borocarbides　is　systematically　studied,　which　clearly　explains　the　reason　of　continuous　reticular　formation　of　borocarbide.　Cr-rich　borocarbide　is　the　proeutecitc　phase,　which　grows　in　the　form　of　faceted-nonfacetedgrowth.　As　the　significant　finding　of　this　work,　the　＂hexagon＂　growth　mechanism　of　Mo-rich　borocarbide　is　discovered.　This　mechanism　feasibly　describes　the　paralleled　lamina　and　faveolated　structure　of　Mo-rich　borocarbide.　These　results　render　a　consideration　for　the　elimination　of　elemental　segregation　through　reasonable　foundry　process　designing.