Inorganic additives-added PEO-based solid composite polymer electrolyte(SCPE)was prepared u-sing solution casting method. The effects of LiNi_(0.8)Co_(0.2)O_2 on the physical and chemical properties of the elec-trolyte were investigated. The products were characterized by X-ray diffraction(XRD), Fourier transform infra-red spectrometer(FFIR)and differential scanning calorimetry(DSC). The electrochemical performances of SCPE were measured. Results show that properties of the SCPE are improved significantly by adding LiNi_(0.8)Co_(0.2)O_2 into PEO polymer electrolyte. Its conductivity reaches 5 × 10~(-4)S/cm(25℃)while retaining good mechanical and processing properties.