Poly(styrene-co-maleic anhydride) (SMA) was modified by commercially available fluorescent dye, 4-amino-N-(2,4-dimethylphenyl)-1,8-naphthalimide, to prepare fluorescent poly(styrene-co-maleimide) (SMI). FT-IR, UV-Vis and fluorescent spectra of this polymer were investigated. The polymer can emit strong yellow-green fluorescence (around 5 10 nm) and its thermal stability and solubility were improved. The number-averaged molecular weight (]U) measured by GPC was about 1.8X10(5) relative to the polystyrene standard and the molecular weight distribution was 1.86. The glass transition temperature (T-g) determined by differential scanning calorimeter (DSC) was 150.8 degreesC, and 17 degreesC higher than the T. (133.7 degreesC) of SMA. The influences of solvent, concentration and quencher on the fluorescent behaviors of SMI are discussed too. (C) 2002 Elsevier Science B.V. All rights reserved.