The method by using distilled water to replace organic solvents to dissolve PEO is simple and the air pollution caused by organic solvents volatilizing will be avoided. The PEO-LiClO₄-SiO₂ polymer electrolyte is prepared by solution-casting method, in which the water is as solvent, the nanometer SiO_2is inorganic filler and the lithium salt is LiClO₄. The effect of nano SiO₂ particles is analyzed. The micro-morphology, crystal structure and electrochemical properties of the electrolyte are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and electrochemical impedance spectra (EIS). The results show that the crystallinity of PEO polymer electrolyte is decreased and the tensile intensity is increased when nanometer SiO_2particles are doped in the polymer electrolyte. The electrochemical stability window is 4.8 V, the highest ionic conductivities (25 ℃) of PEO-LiClO₄-SiO₂(6％) polymer electrolyte is 3.95×10-5S·cm-1and the ionic transference number is 0.29.