The invention discloses a preparation method for an electrode material for a supercapacitor. The preparation method comprises the steps of dispersing a graphene oxide nanobelt into water under an ultrasonic condition to obtain a graphene oxide nanobelt dispersion solution; adding aniline to the graphene oxide nanobelt dispersion solution, stirring and then adding an initator and performing a reaction to obtain a mixed dispersion solution of an intermediate product; adding manganese dioxide nano particles into the mixed dispersion solution of the intermediate product, and then carrying out ultrasonic dispersion to obtain a mixed dispersion solution of the manganese dioxide nano particles/intermediate product; and continuing to add aniline to the mixed dispersion solution of the manganese dioxide nano particles/intermediate product, stirring and reacting, filtering, washing until the pH value is neutral, and drying to obtain graphene nanobelt/manganese dioxide/polyaniline composite material which is used as the electrode material for the supercapacitor. When the graphene nanobelt/manganese dioxide/polyaniline composite material prepared by the method is used as the electrode material for the supercapacitor, an excellent capacitive performance and a long cycle life are represented.