The invention relates to a preparation method of a graphene-grafted polyaniline composite material which can be applied to electrochemical energy storage. The preparation method comprises the following steps of: preparation of carboxyl-functionalized graphene oxide, preparation of amino-functionalized graphene and preparation of the graphene-grafted polyaniline. The preparation method has the advantages that the preparation method of the graphene-grafted polyaniline composite material is novel and unique.