Abstract: A soy protein hydrogel electrolyte for lithium ion-conducting was synthesized with using soybean protein isolate(SPI) and acrylamide(AAm) as raw materials, ammonium persulfate(APS) as initiator, N, N'-methylenebisacrylamide(MBAA) as covalent crosslinker, lithium chloride as electrolyte, and N, N, N, N'-tetramethylene ethylenedia mine(TEMED) as accelerator. The mechanical properties of the hydrogel electrolyte and the electrochemical properties of the solid-state supercapacitor prepared from this hydrogel electrolyte were investigated. The results showed that the hydrogel electrolyte had excellent elasticity and fatigue resistance, because the sliding friction and plastic deformation of soybean protein nanoparticles could effectively disperse the applied stress and dissipate energy, and the polyacrylamide network could maintain the shape. The stress retention rate of hydrogel electrolyte maintained over 100% after experiencing 80% compressive-strain for 100 compression cycles. The plastic deformation was less than 7% and the energy loss coefficient was less than 0.2. In addition, the hydrogel electrolyte had high ionic conductivity, and it could be assembled with polypyrrole/carbon nanotube(PPy/CNTs) paper composite electrode to form a solid supercapacitor. When the water content of the hydrogel electrolyte increased from 60% to 90%, the specific capacitance of the device which was calculated by GCD method increased from 38 F/g to 107 F/g; at the current density of 1.2 A/g, the energy densities of supercapacitors were 3.95-6.86 W·h/kg, the power densities were 206.69-226.99 W/kg. Compared with the reported energy density and power density of supercapacitors, the results showed that the device had the advantages of high energy density and high power density, which provided an effective way and method for the application of hydrogel electrolyte in flexible compressible energy storage devices.