A green physical route for producing novel multifunctional polyvinyl alcohol/kappa-carrageenan alkaline gel polymer electrolyte is developed, which is based on double-network physical cross-linked hydrogel. The alkaline gel polymer electrolyte has excellent tensile stress (2.22 MPa), stretchability (12.43 mm/mm) and ionic conductivity (0.21 S/cm). In this study, KOH is served as not only ionic donator but also cross-linking agent. A supercapacitor is assembled from polyvinyl alcohol/kappa-carrageenan alkaline gel polymer electrolyte and activated carbon electrodes, which exhibits ideal electrochemistry behavior. The electrode specific capacitance is 470 F/g at 0.5 A/g, and retains above 95% after 2000 charge/discharge cycles. Additionally, the electro-chemical performance of supercapacitor under different tensile deformations (<= 200%), bending angles (0-230 degrees) and temperatures (>= -40 degrees C) displays a slightly reduction, indicating that the supercapacitor possesses good flexibility and low temperature resistance. These findings are desirable for applications in supercapacitor devices of flexibility or low working temperature.