Using bacterial cellulose (BC), polyvinyl alcohol (PVA) as raw materials, the superstretched gel electrolyte was prepared by 3D printing and freeze-thaw cycle method. The physical, electrochemical and tensile properties of gel electrolytes were characterized by SEM, contact angle measurement, XRD, EIS and tensile test. The experimental results show that when m(BC)∶m(PVA)=0.6∶1, the gel electrolyte prepared based on 3D printing has a stable three-dimensional network structure, excellent tensile properties and electrochemical performance, the tensile strength can reach 0.9 MPa, and the elongation at break can reach 961%, the ionic conductivity is 1.10×10-1 S/cm. The gel electrolyte is applied to flexible aluminum-air battery, the power density can reach 21 mW/cm2. When the current density of aluminum-air battery is 20 mA/cm2, the specific capacity of aluminum anode is 1124 mA?h/g, and the battery can discharge stably for 90 minutes.