A gel polymer composite electrolyte, a polymer lithium ion battery comprising the gel polymer composite electrolyte and methods of preparing the polymer lithium ion battery are provided. The gel polymer composite electrolyte is formed by swelling after a polymer membrane absorbs an electrolyte, wherein the polymer membrane is formed by thermocuring a polymer mixture comprising an acrylic emulsion, water and ammonia water, and the acrylic emulsion has a glass transition temperature ranging from about −30° C. to about 50° C.