A macromolecule plasticized interpenetrating polymer networks (IPNs) polymer is attempted to develop solid-state polymer electrolyte for lithium-ion batteries. This IPN polymer electrolyte membrane is prepared by a simple in situ UV-curing method, using PEG350mA, PEG200diA, plasticizer and LiClO4 mixture as starting materials. The plasticizer, a six-arm star macromolecule SM400, which is synthesized from phloroglucinol, phosphorus oxychloride and methyl polyethylene glycol (MPEG, M w =400), is found to be effective to improve the ionic conductivity of the IPN electrolytes. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) are used to characterize the IPN based solid state polymer electrolytes. The electrolyte of SM400 (30wt.%)–IPN–LiClO4 (5wt.%) shows the ionic conductivity of 6.06×10−5 Scm−1 at room temperature. A Li/SPEs/LiFePO4 coin cell shows acceptable charge/discharge performance. The proposed attempt paves a potential way to develop solid state polymer electrolytes for Li-ion batteries.