Nitrogen doped three-dimensional graphene (N-3DG) with improved catalytic activities and optimized pore structure is prepared through facile hydrothermal and subsequent annealing processes. When employed as a novel free-standing cathode for Li-O2 batteries, its special three-dimensional structure with increased active sites, large pore volume and numerous available macropores and mesopores effectively facilitates the discharge products deposition, oxygen diffusion and electrolyte infiltration. Compared with pristine three-dimensional graphene (3DG), N-3DG delivers a higher specific capacity of 7300mAhg−1 at the current density of 50mAg−1 and better cycling stability.