ThispapeerstudiestheknowndensitytheoremofArrow-Barankin-Blackwell.Thefollowingmainresultisobtained:IfXisaHausdorfflocallyconvexTopologicalspaceandCbelongtoXisaclosedconvexconewithboundedbase,thenforeverynonemptyweaklycompactconvexsubsetA,thesetofpositiveproperefficientpointsofAisdenseinthesetofefficientpointsofA.