Carbon flakes with a specific surface area of 3010 m(2) g(-1), a pore volume of 2.756 cm(3) g(-1) and an ultrahigh mesoporous volumetric ratio of 97.6% were prepared from tubular kapok fibers through a simple low-temperature pre-carbonization and KOH activation process. The low-temperature pre-carbonization in air was effectively dewaxed the biomass and the thus obtained thin precursor was adequately wetted and etched by KOH, both of which might have resulted in the much improved textural properties. When used as electrode materials of symmetric supercapacitors in organic electrolyte, the carbon flakes displayed high energy density at high power density, e.g. 24 Wh kg(-1) at 24,029 W kg(-1), which was among the best values reported so far on biomassderived porous carbon electrodes. The results reported in this work indicated that both the selection of bio-resources and pre-carbonization treatment were important for preparation of carbonaceous electrode materials with tailored texture properties and enhanced electrochemical energy storage performance.