The invention discloses a preparation method of a lotus leaf carbon-based supercapacitor electrode material. The preparation method comprises the following steps: cleaning lotus leaves, and drying the lotus leaves; placing the dried lotus leaves into a high temperature furnace, carbonizing the lotus leaves at high temperature under the protection of argon, and obtaining lotus leaf carbon; grinding the lotus leaf carbon into powder, sieving, and obtaining lotus leaf carbon powder; introducing a physical activating agent into the lotus leaf carbon powder, activating at high temperature, naturally cooling, and obtaining an activated lotus leaf carbon material; separately soaking the lotus leaf carbon material with an acid solution and an alkaline solution, and drying to obtain the lotus leaf carbon-based supercapacitor electrode material. The preparation method provided by the invention has the characteristics of simplicity and ease in operation, high repeatability, low cost and no environmental pollution. The lotus leaf carbon material prepared by utilizing the method is used as the supercapacitor electrode material, so that the specific surface area of the material can be effectively increased by utilizing the carbonization and activation preparation method, the specific capacity of the supercapacitor is further increased, and the cycle performance is improved.