The invention discloses a stretchable supercapacitor with a stainless steel spring adopted as a base. The stretchable supercapacitor includes a stainless steel spring, an inner-layer electrode, an outer-layer electrode, and a gel electrolyte, wherein the stainless steel spring is adopted as the base of the stretchable supercapacitor, the inner-layer electrode and the outer-layer electrode are formed on the surface of the spring through in-situ growth or coat the surface of the spring, and the gel electrolyte is located between the two electrodes; the whole device is encapsulated with a flexible polymer material, so that the leak of the electrolyte can be prevented; the stainless steel spring, on the one hand, is adopted as a current collector of the inner-layer electrode, and on the otherhand, provides excellent stretchability for the device; the inner-layer electrode is made of a material such as a carbon material, a metal oxide and conductive polymer; the electrolyte is made of a polymer/electrolyte gel system such as PVA/H2SO4 and PVA/H3PO4; and carbon nanotubes or MXenes are wound so as to form the outer-layer electrode. The supercapacitor of the present invention can work normally under large tensile strain; the expected tensile strain of the supercapacitor can be as high as 100% under premise that the performance of the supercapacitor is not affected; and the outer spaceof the spring structural component can be efficiently utilized. The supercapacitor can be applied to systems such as high-speed train wireless monitoring systems.