Abstract: Phosphorus doped porous carbon was prepared by one-step pyrolysis using sunflower straw as carbon source and phytic acid as phosphorus dopant and active agent. The effect of impregnation ratio, activation temperature and holding time on the yield and iodine adsorption value of phosphorus-doped porous carbon was discussed. The pore structure, surface chemical properties and binding state of doped porous carbon were analyzed by automatic specific surface area analyzer and X-ray photoelectron spectroscopy. The results showed that with the increases of impregnation ratio, activation temperature and holding time, the iodine adsorption value of sunflower stalk-based phosphorus doped porous carbon increased first and then decreased. The activation of phytic acid was conducive to the increase of specific surface area and pore volume of porous carbon. Phytic acid was used as a phosphorus source to achieve phosphorus doping of porous carbon, and the binding types of phosphorus were C—PO₃、C—P—O、C₃—PO、C—P＝O and C—P. Under the optimum conditions, when the impregnation ratio was 2, activation temperature was 900 ℃ and the holding time was 2 h, the specific surface area, total pore volume and iodine adsorption value of phosphorus-doped porous carbon were 992.7 m²/g, 1.33 cm³/g and 1 099.8 mg/g, respectively.