PROBLEM TO BE SOLVED: To provide a sludge dewatering conditioning agent and a deep dewatering method thereof which belong to the technical field of urban sewage and sludge treatment.SOLUTION: The invention discloses the novel sludge conditioning agent. The sludge conditioning agent comprises polyacrylamide and a coal pyrolysis product, namely semicoke. The invention also discloses a method for treating the sludge by using the conditioning agent, the method comprises the following steps: firstly, concentrating and dewatering the sludge by using the conditioning agent, wherein the BOD, COD and SS of supernatant liquor after concentrating and dewatering can meet secondary sewage drain standard, and the water content of the treated sludge is less than 80%; and then, directly filter-pressing and dewatering the concentrated and dewatered sludge, wherein the water content of the treated sludge is less than 50%. The sludge conditioning agent for use in the invention is extremely strong in adsorption capacity, low in cost and excellent in performance; the sludge treatment process is simple, the dewatering time is short and the water content of the sludge is low; the dewatered sludge can be directly recycled without drying and dewatering, so that the sludge dewatering conditioning agent has good application prospect.