Abstract: An approach to regulating the pore size distribution of coal-based activated carbon was proposed and studied by potassiumcatalyzed steam activation. Activated carbons were prepared from coal in the presence of different amounts of KOH in the raw materials, and in the process of which, delicate acid washing was performed to change the amount of Kcontaining compounds left in chars after carbonization and before steam activation. Then, the activated carbons were characterized by nitrogen adsorption, scanning electron microscopy, and XRay energy spectrometry, and their adsorption capacity was determined. Results show that the content of Kcontaining compounds left in the char can be controlled jointly by changing the amount of KOH added to the precursor and subsequent washing with 5% mass fraction acid after carbonization. With increasing amount of KOH, the adsorption capacity of the resulting activated carbon becomes greater. The average pore size of the activated carbons gradually increases from 2.379 to 2.636nm, and the mesoporosity increases from 30.9 to 46.1%. The principles for the regulation of pore size distribution in activated carbon were discussed.