In　order　to　meet　the　requirements　of　the　machining　process　of　cone　screw　of　the　Opposed　Conical　High　Pressure　Seawater　Hydraulic　Pump,　this　work　describes　the　design　process　to　determine　the　theoretical　profile　of　the　tool,　starting　from　the　surface　equation　of　the　cone　screw.　Along　with　the　expression　of　the　theoretical　tool　profile,　the　equation　of　the　contact　line　between　the　cone　screw　and　the　tool　is　established　based　on　the　coordinate　transformation　theory　and　the　space　meshing　theory,　as　well　as　the　surface　equation　and　the　position　relationship　between　the　screw　and　the　tool　during　processing.　By　solving　the　contact　condition　based　on　the　method　of　numerical　discretization　analysis　via　MATLAB,　the　contact　line　trajectory　and　theoretical　tool　profile　curve　are　derived.　The　feasibility　of　the　proposed　method　is　verified　by　an　example　of　tool　profile　design　for　machining　the　screw.　Copyright　©　2018　Editorial　Board　of　Journal　of　Donghua　University,　Shanghai,　China.