Here, we report all-solid-state spiral wire-type stretchable supercapacitors (WSSCs) based on wire-type MnO2/graphene (Gr)/Ni electrode, in which a corroded Ni wire serves as substrate, Gr as buffer layer for depositing of MnO2 and KOH-polyvinyl alcohol gel as the solid-state electrolyte. Through interface engineering (surface corrosion and addition of buffer layer), interface contact, equivalent series resistance (ESR) and electrochemical performance of the wire-type electrode are greatly improved. The WSSC exhibits good electrochemical performance and stretchability. Linear (volumetric) specific capacitance of the spiral WSSC reaches 31.48 mF cm−1 (0.45Fcm−3). Maximum linear energy density (power density) reaches 2.80μWhcm−1 (0.54mWcm−1). The capacitance retention is about 92% after deformed at 100% tensile strain. Furthermore, the spiral WSSC has a smaller size and can be easily integrated with electrical wire in electric equipment as a backup power supply, which avoid damage of device or data as sudden power failure occurs.