The invention discloses a preparation method of active carbon with a photocatalytic function. The preparation method comprises the following steps of taking active carbon, oxazine trichloride (C3N3C13), lithium nitride (Li3N) and the like as main raw materials, and performing processes of heating, pressing and the like in a benzene solvent to prepare the g-C3N4-suppurted active carbon with the photocatalytic function. The g-C3N4-suppurted active carbon can purify pollutants by depending on adsorption performance and catalytic performance under a lighting condition, can purify the pollutants by depending on the adsorption performance of the active carbon under the condition with darkness and insufficient light, and can realize in situ regeneration under illumination, so that the consumption of manpower, material resources and financial resources of a regenerative process is greatly reduced. The successful research of the active carbon plays a role in remission of insufficient supply of active carbon in China.