Abstract: In order to make use of tobacco stalk, activated carbon was prepared from tobacco stalk with carbon dioxide as activator.Effects of CO₂ flux, activation time and temperature on the yield and adsorption property of activated carbon were studied with orthogonal experimentation.The proper conditions were: 800℃, 30 min, CO₂ flux: 3L/min, and the yield was 9.47%.The product's sorption values for iodine and methylene blue were 1079.26mg/g and 67.5mg/g, respectively.The nitrogen adsorption isothermal curve of the activated carbon was determined and its pore structure was characterized with BET method, H-K equation, D-A equation and theory of density function.The results showed that the obtained activated carbon was of micropore type with BET specific surface area of 761m2/g, total pore volume of 0.3521cm³/g.Of the total pore volume, micropores' volume accounted for 95.54%, mesopores' volume 3.85% and macropores' volume 0.61%.The microstructure of the activated carbon was analyzed by electronic microprobe and transmission electronic microscopy, the results were comparable with that determined by nitrogen adsorption.