Temperature-induced phase transitions of someN−isopropylacrylamide (NIPAM) copolymers in aqueous solutions were studied with 9-(4-N,N− dimethylaminophenyl)phenanthrene (DP) as an intramolecular fluorescence probe. Lower critical solution temperature (LCST) of DP-labeled NIPAM copolymers depends on the properties and contents of comonomers incorporated in the NIPAM copolymers, i.e., a hydrophobic comonomer such as methyl methacrylate (MMA) lowers the LCST, and a hydrophilic comonomer such as methacrylic acid (MAA) raises it. The higher contents of comonomers, the bigger changes of the LCST. And the micro-environments of the NIPAM copolymers in aqueous solutions also depend on them. The temperature-induced phase transitions of NIPAM copolymers withN-n−propylacrylamide (NNPAM), andN−isopropylmethacrylamide (NIPMAM) appear to be very sharp as well as that of NIPAM homopolymer aqueous solution and their LCST values are good correlated with their copolymer compositions.