We investigated the miscibility of poly(methyl methacrylate) (PMMA) and random copolymers of tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV) blends and their interfacial adhesion as part of the development of cladding materials for PMMA based plastic optical fiber. Three different types of THV with different copolymer composition were used as candidate for them. PMMA/THV blends being melt-mixed at 240℃ showed typical immiscible morphology and the glass transition temperatures of the component polymers did not change after mixing.