Abstract: A series of activated carbons were prepared from tobacco stems as raw materials and potassium hydroxide as activating agent by a one-step carbonization process. The effects of the preparation variables on the yield and adsorption properties of activated carbon were systematically studied via orthogonal experiments, and the optimum condition was obtained. The iodine value of the activated carbon prepared under the optimum condition was 1198.27mg/g and the methylene blue adsorption was 3 times of that the first grade product specified in the National Standard. Furthermore, the nitrogen isotherm of the sample was determined. The porous structures were investigated with the Horvath-Kawazoe equations and density function theory. The results of the pore structures analysis was consistent with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) study.