The invention discloses a method for converting tree leaves into activated carbon by utilizing plasma combined with an activating agent, relating to the field of plant processing. The method comprises the following steps: pretreating; dipping with the activating agent; performing drying and carbonizing treatment; cleaning; performing surface activating treatment; utilizing the high temperature of the plasma as a heat source for carbonizing; and combining with an activating method with a chemical activating agent and performing high-temperature surface treatment again, thereby efficiently converting the tree leaves into high-performance activated carbon.