Preparation and performance of poly(acrylonitrile-methylmethacrylate) based microporous gel electrolyte for Li-ion batteries were studied. The poly(acrylonitrile-methyl methacrylate (P(AMMA)) was synthesized by suspension polymerization, and poly(acrylonitrile-methyl methacrylate) microporous polymer membrane with 0.03~0.1mm was prepared by phase inversion technique. The gel electrolyte was obtained by putting the P(AMMA) microporous polymer membrane in a liquid electrolyte, which was a solution of 1.0 M LiPF6 dissolved in a 1:1 (v/v) mixture of ethylene carbonate (EC) and diethylene carbonate (DEC, and heated at 60°C for 2 hours. The microporous gel electrolyte gelled with 325 wt.% of liquid electrolyte vs. the dried membrane presented an ionic conductivity of 7.52 × 10-4 S/cm at 25°C. The coin test battery with the microporous gel electrolyte showed a good cycling performance. The discharge capacity retention was above 88% at 0.1C rate at the 50th cycle.