Abstract: The activated carbon was prepared from kenaf rod core by mechanical force pretreatment process and conventional process with phosphoric acid as activator. The effects of activation time on the yield, adsorption performance of the kenaf rod based-activated carbon were discussed. The pore structure characteristics were characterized by specific surface area and pore size analyzer and the surface functional groups were characterized by Fourier transform infrared spectroscopy. The results showed that compared with the conventional process, the mechanical force pretreatment process made phosphoric acid permeate into the inner layer of raw material to strengthen the activation efficiency, which improved the yield, adsorption performance, BET specific surface area and pore volume of kenaf rod based-activated carbon. Under the activation time 90 min, the yield, iodine adsorption value, methylene blue adsorption value, BET specific surface area and total pore volume of the activated carbon prepared by mechanical force pretreatment process were 50.24%, 1 024 mg/g, 275 mg/g, 1 625.42 m2/g and 0.762 cm3/g, respectively. According to pore size analysis, activated carbons prepared by the two methods were mainly microporous and contained a certain number of mesopores. It was known from infrared spectrum analysis that the mechanical force pretreatment process didn't destroy the basic structure of activated carbon. The surface of kenaf rod based-activated carbon prepared by the two methods contained oxygen-containing functional groups, such as —OH,C—O and C=O groups.