Abstract: Block copolymers PMMAbPS were synthesized through atom transfer radical polymerization(ATRP) and characterized by FT-IR, 1H-NMR, and gel permeation chromatography(GPC). The numberaverage molecular weight and molecular weight distribution were 2.69×105 and 1.53, respectively. A series of PMMA-b-PS based gel polymer electrolytes(GPE) membranes were prepared by solution casting technique. The ion conductivity of GPE membranes was characterized by AC impedance. It was found that 40%(mass fraction) PMMA-b-PS was good for performance of the GPE film with conductivity of 8.82×10-5 S/cm. TGA results of the GPE showed that the thermal decomposition temperature of block copolymer gel electrolyte was 139 °C at 5% mass loss which was 49 °C higher than that of PMMA based GPE.