The invention provides a preparation method for an electrode material of a supercapacitor. Poly (p-phenylene terephthalamide) fibers are stirred with dimethyl sulfoxide and potassium hydroxide until the mixture is fully dissolved to obtain a Kevlar nanofiber dimethyl sulfoxide dispersion liquid; then a manganese acetate solution is added and stirred uniformly to obtain a flocculent dispersion liquid; then the flocculent dispersion liquid is subjected to vacuum filtration to be put in a freezing dryer to be frozen and dried; and finally the material is put into a tubular furnace to be subjected to high-temperature calcining to obtain the electrode material of the supercapacitor. The electrode material obtained by the method is excellent in electrochemical performance and relatively high in specific capacitance, represents a rapid-charging and slow-discharging performance in a constant-current charging-discharging process under a relatively high current density, has extremely high commercial popularization value, and has relatively high development prospect in the energy storage field in the future.