A novel composite porous membrane is obtained by phase inversion using the prepared poly(acrylonitrile-N-vinylpyrrolidone) (P(AN-NVP)) as a polymer matrix, which absorbs liquid electrolyte to form the corresponding P(AN-NVP) based gel polymer electrolyte (GPE). A large number of test methods are used to characterize the overall performances of P(AN-NVP) membranes. These results show that when AN and NVP are copolymerized at a mass ratio of 6:1, the prepared P(AN-NVP) copolymer film possesses membrane structure that riching in three-dimensional interpenetrating micropores, and has lower crystallinity and satisfactory mechanical properties compared with that of pure PAN membrane, which greatly promotes the electrochemical performances of the corresponding GPE: the supreme liquid electrolyte uptake of 876.67 wt% and higher ion conductivity of 4.54 × 10−3 S cm−1 at room temperature, a significantly enhanced lithium ion transference number of 0.55, a broader electrochemical stability window of 5.11 V (vs. Li/Li+) and relatively stable interfacial compatibility. The higher charge-discharge capacity of 114.8 mAh g−1 at 0.2C, and the great capacity retention of 95.4% at 0.5C after 70 cycles with the coulomb efficiency of 98%. In addition, the GPE-6-1 based lithium ion battery exhibits excellent cycle performance and a weak voltage hysteresis of 5.8 mV over a 600 h Li plating/stripping process at current density of 0.5 mA cm−2 and capacity of 0.5 mAh cm−2.