The invention relates to a method for preparing a composite electrode material of a super capacitor. The method comprises the following steps of: (1) ultrasonically dispersing graphite, sodium nitrate and concentrated sulfuric acid into an ice bath, adding potassium hypermanganate, magnetically stirring, adding deionized water, magnetically stirring to make a mixture uniform, re-adding the deionized water, stirring at constant temperature, reacting in a water bath, cooling, adding hydrogen peroxide, centrifugally washing, freezing and drying in vacuum, and thus obtaining graphite oxide; (2) dispersing the graphite oxide, nickel salt and cobalt salt into a solvent, and performing solvothermal reaction to synthesize a Ni(OH)2/CoO/rGO composite material; and (3) uniformly mixing a Ni(OH)2/CoO reduction graphene oxide composite material, carbon black and polyvinylidene fluoride, stirring at room temperature, uniformly coating on the surface of nickel foam, drying in vacuum, and thus obtaining the composite electrode material of the super capacitor. The method is easy to operate and low in equipment using requirement. Raw materials are easily obtained, low in toxicity and low in cost. A novel method is provided for preparation of a nanosheet composite electrode material.