Abstract: Gel polymer electrolytes comprising 1-butyl-3-methylimidazolium-chloride-ZnCl₂[BMM](Cl-ZnCl₂) Lewis acid room temperature ionic liquid in PMMA matrix were prepared by means of in situ radical polymerization of vinyl monomers.The polymer matrix was formed by free radical polymerization of methyl methacrylate (MMA) monomers.Structure and properities of the product were studied by FTIR,AC,TG,GPC.The interactions and structure changes of [BMM]Cl-ZnCl₂/PMMA were investigated by FTIR,which showed composites structure.When n([BMM]Cl-ZnCl₂):n(MMA) is 7:3,the gel polymer electrolyte showed the maximum ionic conductivity of about 0.36×10^-3 S/cm at room temperature.The gel polymer electrolytes had greater thermal stability than the traditional non-aqueous electrolyte systems including organic solvent.They exhibited high decomposition temperatures above 286℃.M_w/M_n ratios of the gel polymer electrolytes were decresed as [BMM]Cl-ZnCl₂ mol content increased,which showed narrower molecular mass distribution.Ionic conductivities of the gel polymer electrolytes were increased as [BMM]Cl-ZnCl₂ mol content increased.