The invention discloses a method for preparing supercapacitor electrode material by grapes. The grapes are used as a carbon material precursor, the electrode material with a three-dimensional multi-stage pore structure and a graphene-like structure is quickly prepared by adding different modifiers and combining low-temperature pre-carbonization with high-temperature carbonization activation, and the cycling performance of the electrode material is enhanced through three-dimensional net structure and the graphene-like structure and different capacitor specific capacitance can be realized. The common biomass grape in life is used as the raw material, the grape is rich in source and low in price, the preparation method has the advantages of simple operation, high repeatability and no pollution to the environment and meets the requirements of sustainable development and environmental protection and can effectively reduce the cost of preparing the electrode material. The prepared biomass grape-based electrode material has high specific capacitance and good cycling stability and is an ideal supercapacitor electrode material and has a broad development prospect.