The three-dimensional porous structure of a material can trap the propagating electromagnetic waves by multiple reflections and scatterings, thereby improving the microwave absorption properties. The highly ordered and interconnected porous NaY zeolites can serve as the templates to prepare the three-dimensional graphene (3DG). A high defect density of 13.4-23.7 x 10(10) cm(-2) was obtained in the 3DG due to the incomplete replication. Simultaneously, the broken asymmetry of space charges in the defect sites will lead to the separation of space charges and the formation of electric dipoles, which results in significantly enhanced dielectric performance and microwave absorption. Consequently, owing to the porous structure and high specific surface area, the effective absorption band of the 3DG attains a large width of 14.3 GHz (3.7-18 GHz) with the absorber thicknesses located in 2-5 mm. The microwave absorption performance of 3DG is much superior to that of multilayer graphene with a two-dimensional structure. Hence, this ultralight 3DG can act as a promising microwave absorption material and probably gifts other physical applications in the future.