Two-types of ionically modified multi-walled carbon nanotube (MWNTs) based sensors were developed by radiationinduced graft polymerization using vinyl monomers such as 3-(butyl imidazol)-2-(hydroxyl)propyl methyl methacrylate and 1-[(4-ethenylphenyl)methyl]-3-buthyl-imidazolium chloride with ionic properties, in aqueous solution at room temperature. Subsequently, the tyrosinase-immobilized biosensor was fabricated by a hand-casting of the ionic property-modified MWNTs, tyrosinase, and chitosan solution as a binder onto ITO glass surface. The sensing ranges of the tyrosinase-biosensor for phenol in phosphate buffer solution was in the range of 0.005~0.2 mM. The total phenolic compounds mainly such as caffeine of the tyrosinase-immobilized biosensor for commercial coffee were also determined.