Abstract: Novel mesoporous carbons were prepared by the simple pyrolysis of block-copolymers, polyacrylonitrile-b-polystyrene-b-polyacrylonitrile (PAN-b-PS-b-PAN), in which PAN generates a carbon network and PS is released to form mesopores after pyrolysis. The block-copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and the molecular weight of each polymer block can be designed to tailor the porous structure of the mesoporous carbons. The carbons have high specific surface areas and a well-controlled mesopore size. The best mesoporous carbon has a high specific capacitance of 185 F·g^-1 at 0.625 A·g^-1 with a high power capability and a remarkable cycle stability in 2 mol/L KOH aqueous electrolyte.