The invention discloses a method for preparing activated carbon by taking ionic liquid as an activator, which is used for preparing high-specific-surface-area activated carbon by taking ionic liquid as an activator with a wood or bamboo raw material. The iodine sorption value of the activated carbon prepared by using the method disclosed by the invention can reach 1360-1870 mg/g, and the specific surface area of the activated carbon reaches 2580-3650 m<2>/g; the activated carbon is less in activator consumption and environment-friendly, and has simple requirements on equipment; and the problem that the traditional chemical methods for preparing activated carbon is implemented by taking strong acids (H2SO4 and H3PO4) and strong alkalis (KOH and NaOH) and the like as activators, so that the pollution to the environment is heavy, and the corrosion on equipment is serious, and the like is avoided, therefore, the method disclosed by the invention has significant economic and social benefits.