Thermally induced phase separation (TIPS) process was employed to prepare microporous poly (vinylidene fluoride)/poly (methyl methacrylate) (PVDF/PMMA) blend membranes using sulfolane as the diluent. Then they were immersed in liquid electrolyte to form polymer electrolytes. The effect of PMMA on the morphology and the crystallinity of blend membranes was studied. It was found that phase separation between PVDF and PMMA occurred when PMMA content was 40 wt.%. The addition of PMMA increased porosity and decreased the crystallinity, which in turn enhanced electrolyte uptake of blend membrane and the ionic conductivity of corresponding polymer electrolyte. The maximum ionic conductivity was 2.45 × 10− 3Scm− 1 at 20 °C.