A simple method has been developed to prepare graphene/activated carbon (AC) nanosheet composite as high-performance electrode material for supercapacitor. Glucose solution containing dispersed graphite oxide (GO) sheets is hydrothermally carbonized to form a brown char-like intermediate product, and finally converts to porous nanosheet composite by two-step chemical activation using KOH. In this composite, a layer of porous AC coats on graphene to from wrinkled nanosheet structure, with length of several micrometers and thickness of tens of nanometer. The composite has a relatively high packing density of similar to 0.3 g cm(-3) and large specific surface area of 2106 m(2) g(-1), as well as containing plenty of mesopores. It exhibits specific capacitance up to 210 F g(-1) in aqueous electrolyte and 103 F g(-1) in organic electrolyte, respectively, and the specific capacitance decreases by only 5.3% after 5000 cycles. These results indicate that the porous graphene/AC nanosheet composite prepared by hydrothermal carbonization and chemical activation can be applied for high performance supercapacitors. (C) 2014 Elsevier B.V. All rights reserved.