The invention relates to a preparation method of polystyrene modified three-dimensional graphene foam, belonging to the field of functional materials. The preparation method comprises the following steps: adding a polystyrene-containing cyclohexane solution into an oxidized graphene solution while stirring, then adding a sodium dodecyl sulfate water solution, and continuing to stir, so as to obtain a uniformly mixed solution; adding the obtained uniformly mixed solution in liquid nitrogen to be frozen, taking out the uniformly mixed solution out of liquid nitrogen, and then freeze-drying, so as to obtain polystyrene modified three-dimensional graphene aerogel; and carrying out annealing treatment on the polystyrene modified three-dimensional graphene aerogel at the protective atmosphere of hydrogen-argon mixed gas, so as to obtain the polystyrene modified three-dimensional graphene foam. The preparation method is simple and is applicable to large-scale production, and the operation is easy; and the prepared polystyrene modified three-dimensional graphene foam is of an ordered honeycomb structure, is light and has super-compression performance and excellent electrochemical performance.