The nanoscale microporous carbide-derived carbon (nano-CDC) is synthesized by chlorination of silicon carbide nano-powder with a particle diameter around 60 nm and further pore-tuned by KOH activation with different KOH/nano-CDC ratios. Based on the higher specific surface area (SSA), a hierarchical micro- and meso-pore structure (especially for the greatly produced mesopores), and the shorter inherent ion transport distance within porous nano-carbons, the KOH-activated nano-CDC exhibits superior supercapacitive performances. Its specific capacitance is up to 141 F g(-1), 156% increase compared with that of pristine nano-CDC (54 F g(-1)). Most interestingly, the cyclic voltammogram curve of the activated nano-CDC can keep a rectangular-like shape even at a scan rate of 5000 mV s(-1), exhibiting significantly better power performance. This work confirms that constructing favorable pore structure in nanometersized porous carbons is an effective strategy for fabricating high-power supercapacitors. (C) 2015 Elsevier Ltd. All rights reserved.