The graft copolymer containing a polythiophene (PT) backbone and polystyrene branches with superior solubility and processability was obtained by the atom transfer radical polymerization (ATRP) of styrene from the initiating sites on the PT backbone. The grafted PS branches could separate the PT chains and form a PS matrix for effectively trapping the PT in a solution conformation, which was advantageous to the improvement of fluorescent efficiency in the solid state.