The invention relates to a cotton fabric-based flexible electrode material preparation method. Cotton fabric is activated in a sodium hydroxide aqueous solution and is then soaked in a manganese acetate aqueous solution; a potassium permanganate aqueous solution is then added for processing, washing to neutral is performed, and cotton fabric deposited with manganese dioxide is obtained; the abovefabric is then soaked in a graphene oxide hydrosol for processing; and finally, a thermal reduction process is adopted to reduce the graphene oxide on the surface of the cotton fabric to graphene, anda cotton fabric-based flexible electrode material is obtained. The method provided in the invention overcomes shortcomings in the prior art, and the prepared cotton fabric-based flexible electrode material has breathable, flexible and stretchable characteristics of the cotton fabric- and can also keep good electrochemical performance in a stretching state.