The invention discloses an aqueous zinc ion battery composite electrolyte membrane and a preparation and application method thereof. The prepared zinc alginate-based polymer composite gel electrolytemembrane has a homogeneous three-dimensional layered cross-linking network structure and high ion conductivity. According to the preparation method, the polysaccharide sodium alginate-based material and the zinc ion are utilized, and the zinc ion cross-linking electrolyte membrane is formed in a weak acid or neutral medium through stacking after the sodium-zinc ion exchange reaction. The electrolyte membrane prepared by the method has both excellent physical and electrochemical properties, the problems of negative electrode zinc dendrites and zinc corrosion can be effectively suppressed, and the method is simple and fast, low in cost, environmentally friendly and controllable in condition and is particularly suitable for low-cost large-scale energy storage zinc ion battery systems and alsosuitable for preparing flexible aqueous system zinc ion batteries in flexible devices.