It is a compelling challenge to both improve ionic conductivity and mechanical properties in polymeric electrolytes, and to accomplish it through a simple processing method. This study reveals that poly(ethylene oxide)-block-polyethylene (PEO-b-PE) possesses a capability for enhancing the multiple performances of PEO-based polymer electrolyte, i.e., it functions as a multi-functional miscible filler for obtaining poly(ethylene oxide)(PEO)/lithium perchlorate (LiClO4) having such enhanced performances. In this paper, remarkable enhancements in both ionic conductivity and mechanical properties are presented and analyzed. Investigations on the ion transportation behavior in the polymer electrolytes through optical micrograph, X-ray diffraction, Fourier transform infrared, and dielectric spectrum analyses revealed that the ionic conductivity of a ternary polymer electrolyte, PEO/PEO-b-PE/LiClO4, was enhanced by an order of magnitude with the addition of this copolymer. The results of tensile tests showed the ultimate stress of the ternary polymer electrolyte increased to 7.29MPa, modulus 114.21MPa, and breaking strain 1142.53%, which are 2252%, 688% and 274% higher than that of PEO/LiClO4, respectively. This study highlights that this kind of copolymer is a promising candidate for high performance solid polymer electrolytes in lithium battery applications.