A method of preparing active carbon with waste coke powder is as follows: first, grinding the raw material of waste coke powder into 0.5-0.05mm, then mixing the coke powder with potassium nitrate with the mass ratio of 5:1, adding proper amount of water and uniformly stirring the mixture into paste, then moving the paste into a heating furnace and raising the temperature to 600 DEG C under the protection of nitrogen, after that, keeping the temperature for 30 minutes and then cooling to the room temperature to get pretreated coke powder; mixing the pretreated coke powder with activator with the mass ratio of 1:6, wherein, the activator consists of potassium hydroxide and calcium carbonate which have the mass ratio of 3:1, then adding proper amount of water and uniformly stirring the mixture, then moving the mixture into the heating furnace and raising the temperature to 650-900 DEG C under the protection of nitrogen, keeping the temperature for 40-100 minutes and then cooling to the room temperature to get crude active carbon; soaking the crude active carbon in 10% HF solution of 30ml for 3-4 hours, then washing and drying by hot deionized water to get the refined coke powder active carbon.