Multi-walled carbon nanotubes (MWCNTs) were supramolecularly functionalized by pyrene-derivatized hydrolyzed poly(styrene-co-maleic anhydride) (pyrene-HSMA) in aqueous solution. The MWCNTs/pyrene-HSMA conjugates were found to exhibit a solvent-dependent fluorescence property by photoluminescence measurements. The fluorescence intensity of the MWCNTs/pyrene-HSMA conjugate was used as a probe to estimate the interaction between polymer and MWCNTs in solvents. The polymer conformation around the MWCNTs was demonstrated by atomic force microscopy. We suggested that pyrene-HSMA functionalized MWCNTs in a non-wrapping mode, and that the conformation change of the polymer around the MWCNTs resulted in the solvent-dependent fluorescence property. The dispersion state of the MWCNTs/pyrene-HSMA conjugate in various solvents was also investigated by transmission electron microscopy. The fluorescence responses of the MWCNTs/pyrene-HSMA conjugate to pH value and temperature were studied as well.