The crosslinked gel polymer electrolytes (CPEs) were fabricated via combination of physical blending and chemical cross-linking procedures. PVDF/PS-PEO-PS precursor membranes were prepared by phase inversion technique and then followed by in situ cross-linking process based on the Friedel-Crafts reaction of aromatic groups. The morphology, thermal stability and electrochemical properties of CPEs were characterized and the effect of PEO chain length of the copolymers on the properties of CPEs was discussed. The results show that the porosity and thermal stability of CPE membranes are greatly improved compared with pure PVDF membranes. The CPE-2 membrane shows the highest porosity (72.3%) and remains stable pore configuration up to 300 ℃ with little dimensional shrinkage. When assembled into batteries, CPE-2 shows a high ionic conductivity (2.09 mS/cm) and good charge-discharge performance.