The invention relates to the field of battery materials, and in particular discloses a method for preparing three-dimensional porous graphene. The method comprises the following steps: S1, putting a cross-linking agent into a graphene oxide dispersion, and performing a hydrothermal reaction for 8-10 hours at 120-180 DEG C so as to obtain a mixed liquid; S2, putting dodecyl dimethyl amine oxide into the mixed liquid at 10-25 DEG C, sufficiently stirring till the components are uniformly mixed, further adding ammonium bicarbonate and ammonium nitrate, slowly stirring for 0.5-1 hour, performing freeze-drying for 1-2 days, and taking out; and S3, rapidly pushing the dried object which is taken out into a reducing atmosphere at 200-300 DEG C, performing pre-sintering for 12-24 hours, further heating to 500-700 DEG C, calcining for 3-5 hours, and cooling, thereby obtaining three-dimensional porous graphene. The three-dimensional porous graphene prepared by using the method is sufficiently communicated with pores, is large in specific surface area, stable in three-dimensional structure formed in a lap joint manner and high in conductivity and can be effectively applied to battery materials, and the energy density and the use security of batteries are improved.