Graphitic carbon nitride(g-C3N4),a two-dimensional graphite-like structure,has attracted a considerable amount of attention owing to its high nitrogen content,excellent chemical and thermal stability,special optical features,appealing electronic structure and environmentally friendly features,thus leading to multifunctional catalytic activities for photocatalysis and other energy conversion processes.[1] g-C3N4 is mainly restricted in electrochemical-related applications due to its inherent low electronic conductivity and low surface area.On the other hand,graphene can be used as a versatile building block for self-assembling into specfic architectures,which is essential for converting the remarkable microscopic characteristics of graphene sheets into macroscopic properties of practical significance.[2] It was found that the combination of g-C3N4 with graphene could improve the conductivity and electrocatalytic performance of g-C3N4,which has been explored as a metal-free material for electrocatalysis.[3] We have reported a rational assembly of g-C3N4 and graphene into 3D interconnected networks by a facile one-step hydrothermal method.The resulting well-defined 3D g-C3N4@G induces the hierarchical architecture,thus facilitating the charge transfer and provides a multi-way electron transfer which can effectively accelerate the electrochemical process to achieve high energy storage.Consequently,the as-prepared g-C3N4@G exhibits a significantly enhanced electrochemical capacitance of 264 F g-1 at 0.4 A g-1,representing a nearly more than 75%capacitance improvement in comparison to the pristine graphene hydrogels(152 F g-1).The reported 3D composite materials are much desirable as electrode materials in supercapacitors.