The invention discloses a preparation method for an active carbon with a photocatalysis function. The active carbon with the photocatalysis function is prepared from main raw materials comprising active carbon, dicyandiamide or melamine through processes of mechanical ball milling and high-temperature roasting. The active carbon has an adsorption-photocatalysis difunction and can be regenerated in situ under illumination, so that manpower, material and financial resources are greatly saved in a regeneration process. The preparation method for the active carbon with the photocatalysis function achieves a certain effect in easing insufficient supply of the active carbon in China.