Stimuli-responsive polymers that can achieve intelligent temperature response in ionic liquids have already received widespread attention. In this paper, such a system is applied to gels, incorporating different metal salts to investigate the phase transition behavior of poly(phenethyl methacrylate) (PPhEtMA) in a mixed ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C?MIM[TFSI]) and 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide (C?MIM[TFSI]), and to deeply explore the thermoresponsive phase transition process of PPhEtMA inside the gel. The results show that doping with different metal salt anions and cations can affect the enthalpy of the LCST system and increase the phase transition temperature of PPhEtMA in the ionic liquid to varying degrees; the phase transition temperatures of gels incorporating 1 mol/L NaOTf, 1 mol/L LiOTf, and 1 mol/L Mg(OTf)? are 67 °C, 83 °C, and 96 °C, respectively. FT-IR measurements before and after the phase transition reveal that the key to the thermoresponsive behavior of the gel lies in the fact that heating causes the π-cation interactions between the phenyl rings of PPhEtMA and the imidazolium groups of the ionic liquid to break, and the interaction between Li? and the O=C groups of PPhEtMA also weakens, thereby promoting the precipitation and aggregation of the polymer and the formation of a microphase-separated structure.