A novel perfluorocyclobutyl aromatic ether-based ABA triblock copolymer (A: polystyrene block; B: perfluorocyclobutyl aromatic ether-based fluoropolymer block) was synthesized by combination of atom transfer radical polymerization (ATRP) of styrene and thermal step-growth cycloaddition polymerization of trifluorovinyl monomer. We first synthesized a new ATRP initiator containing the trifluorovinyl group, which can initiate ATRP of styrene in a controlled way to obtain well-defined polystyrene with narrow molecular weight distribution (M-w/M-n < 1.10). The apparent polymerization rate exhibited first-order relation with respect to the concentration of monomer and the molecular weight increases linearly with the conversion of monomer. Second, fluoropolymer containing a perfluorocyclobutyl aromatic ether unit was prepared by solution polymerization and followed by reacting with ATRP initiator containing a trifluorovinyl group to get ATRP macroinitiator with two initiation groups at both ends. The macroinitiator-initiated ATRP of styrene to obtain ABA triblock copolymer. The copolymer shows excellent solubility in conventional solvents.