The invention relates to three-dimensional network graphene for a lithium battery and a preparing method thereof. The preparing method of the three-dimensional network graphene for the lithium battery comprises the steps that firstly, high-purity expanded graphite, an anion type organic surface active agent, a dispersing agent, an antifoaming agent and a solvent are fully mixed, so that thick few-layer graphene slurry is obtained; liquid swelling high polymer materials are added, composite slurry is obtained after even mixing, and the composite slurry is coated in holes of porous foam materials; finally, the porous foam materials are fully carbonized and then are further processed, so that three-dimensional network graphene powder is obtained. The graphene prepared through the method is of a porous network structure on the microscopic scale, and thus the graphene is high in specific surface area, high in conductivity, high in heat conductivity and good in electrolyte wettability; when the graphene is mixed into positive electrode and negative electrode materials of the lithium battery for manufacturing pole pieces, the electron conduction can be effectively improved, the internal resistance of the battery can be greatly lowered, the amount of heat generated when the battery is charged and discharged is educed, the power density, the energy density and the safety of the battery are further improved, and the service life of the battery is prolonged.