The invention discloses a preparation method of a supercapacitor electrode material based on two-dimensional carbon nanosheets. Starch paste is heated on foamed nickel at 400 DEG C, so that a two-dimensional amorphous carbon nanosheet can be synthesized; the two-dimensional amorphous carbon nanosheet is coated with an active metal salt compound film, so that an obtained mixed electrode shows an excellent electron collection rate. Due to the synergistic effect of the active metal compound and the two-dimensional amorphous carbon nanosheet, the designed electrode shows high specific capacitance,good rate capability and excellent cycling stability. With the preparation method adopted, a new strategy is provided for the manufacturing of the two-dimensional carbon nanosheet, and a bright prospect is provided for the application of a supercapacitor.