The photophysical and solution properties of naphthalene-labeled styrene/N,N-dimethyl maleimido propylammonium propane sulfonate copolymer, poly(SDMPAPS)/NA, were studied in terms of fluorescence, cloud paint, and viscosity measurements. The ratio of intensities of the excimer and monomer fluorescence (I-E/I-M) was shown as a function of polymer concentration in deionized water. The value of I-E/I-M decreases with an increase in the salt concentration. The addition of anionic surfactants to the aqueous solution of poly(SDMPAPS)/NA can either induce or break the interpolymer aggregation. When the electrolyte concentration increases, the Stern-Volmer quenching constant (K-sv) also increases. The phase behavior of poly(SDMPAPS)/NA shows an upper critical solution temperature around 17 degrees C. The intrinsic viscosity of the poly(SDMPAPS)/NA in the presence of different salts reflects the influence of these salts on the hydrodynamic volume of the polymer chain for poly(SDMPAPS)/NA. A model of the interaction between poly(SDMPAPS)/NA and surfactant in aqueous solution is proposed.