Abstract: A series of activated carbons was prepared using a two-step activation process. The starting glass-like carbon spheres were heated at 500℃ for 3h (first step activation), and then at a low temperature, below 415℃, for different times (second step activation), in a flow of dry air. Their pore structures were evaluated from N2 gas adsorption/desorption isotherms at 77K by BET, αs-plot and BJH methods. The first step of activation generated a few large pores (mesopores and even macropores), on the surface of the spheres, which formed the entrance for the activating reagent gas (air), to increase micropores at a low temperature in the second step of activation. This two-step activation process was found to be an efficient approach to get a comparatively high surface area and a volume of micropores with a high activation yield.