Abstract: Activated carbons (ACs) made from petroleum coke by KOH activation were further treated by microwaves to investigate the effect of microwave-treatment time on the pore structure, the surface properties (functional groups) and the electrochemical properties of the as-made ACs for electrochemical capacitors (ECs). Results show that the specific capacitance and the equivalent series resistance of microwave-treated ACs become smaller with a decrease in the Brunauer-Emmett-Teller surface area and the total pore volume (v_t) of the treated ACs. Compared with the AC sample heated at 1073K for 1h by a conventional heating method, the AC sample treated by microwaves at 700W for only 7min has a pore size distribution with a high (meso- and macropore volume)/v_t ratio and a high carbonyl content, and exhibits a high energy density and powder density as an electrode of ECs. This has clearly shown that the microwave-treatment is a simple and efficient approach to obtain high-performance ACs for ECs.