The invention discloses a method for producing activated carbon by thermally activating a coal tar dreg/sludge mixed fermentation body by using microwaves. The method comprises the steps of: firstly crushing and grinding coal tar dreg into more than 200 meshes, then, mixing the ground coal tar dreg with sludge, and performing aerobic fermentation for 10-20 days; then, adding zinc chloride servingas an activator into the mixed fermentation body, and infiltrating for 12-24h at 70-80 DEG C, wherein the added zinc chloride is 0.5-4 times more than the mixed fermentation body in mass; and finally, carbonizing and activating for 30-120min in a microwave carbonization furnace under a N2 protection condition to obtain coal tar dreg/sludge mixed activated carbon, washing with water till a neutralcondition is achieved, and drying to obtain a product disclosed by the invention. The method disclosed by the invention has the advantages of simplicity and convenience for operation, easiness for control, low cost, high product synthesis rate and favorable product performance, and can be widely applied to industrial wastewater treatment, refractory wastewater treatment, sound insulation, noise reduction, deodorization, oil absorption, lipid suction and other industries.