A pH/temperature-responsive fluorescence polymer, I42D50S8-FL, consisting of N-isopropylacrylamide, N,N-dimethylacrylamide, and sulfamethazineacrylamide was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by activation of terminal carboxyl groups with N-hydroxysuccinimide and reaction with 5-aminofluorescein (FL). I42D50S8-FL exhibited a pH-dependent phase transition across the lower critical solution temperature (LCST), with specific intracellular uptake observed only in weak acidic conditions. I42D50S8-FL has the potential to be applied for the selective imaging of acidic tumor microenvironments.