The invention discloses a method of harmless treatment to residual activated sludge produced by bottom sludge, scum and biochemical treatment units in the petrochemical industry, which comprises: emulsion breaking to the bottom sludge and scum; separation of oil, water and mud of products after emulsion breaking; and recovery of dirty oil at the upper part and sedimentation of mud-water mixture at the lower part, recovery of clear liquor at the upper part, and treatment of coagulation conditioning, flocculation conditioning, sludge concentration, sludge dewatering, sludge drying and sludge incineration to mud-water mixture at the bottom part and the residual activated sludge sequentially. The method can effectively recycle useful oil substances and aluminum-containing compounds in the bottom sludge and scum, purify possibly released malodorous gases in mud produced in the process of storage and disposal, and carry out the treatment such as sludge conditioning, dewatering and drying sequentially to the residual mass hazardous wastes after the recycling treatment, then utilize the current boilers in enterprises to implement the direct incineration treatment. The method has advantages of simple operation and running, safety and reliability, complete resource recovery, controllable water removal, and maximally reducing the environmental pollution.