Nitrogen-doped graphene has attracted increasing attention in recent years. Synthesis of nitrogen-doped 3D graphene with high capacitance and excellent capacitive behavior is highly desirable for high-performance supercapacitor applications. In this study, nitrogen-doped porous 3D graphene was prepared from graphite oxide using the mild one-pot hydrothermal procedure. The p-phenylenediamine and ammonia were selected as the reduction and doping agents, respectively. 3D graphene specimens with various nitrogen doping amounts of 6.52-7.81% were prepared. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and supercapacitor performance were used to investigate the morphologies, structures and capacitance behaviors of the prepared 3D graphene composites. The results indicated that the as-prepared specimens contained different doping nitrogen amounts. NGP-10.6 showed well-connected 3D porous microstructure with largest doping nitrogen content. In turn, nature and content of nitrogen doping provided the graphene with excellent capacitive behavior. The specific capacitance of NGP-10.6 reached 788 F center dot g(-1) at the current density of 0.5 A center dot g(-1) and 296 F center dot g(-1) at 10 A center dot g(-1). Overall, these findings look promising for future applications as outstanding energy storage materials.