The gel polymer electrolytes (GPEs) based on ionic liquid (EMIBF4) and cross-linkable monomer (PEGDA) were prepared for electric double layer capacitors (EDLCs). Although the EDLC with GPE shows lower ionic conductivity, higher interfacial resistance and lower initial specific capacitance than that with liquid electrolyte (LE), it becomes more reliable in the point of cycle life. This enhancement may be responsible for suppressing the electrolyte leakage phenomenon.