The invention relates to a deep dewatering treatment system for sludge, which belongs to the technical field of environmental geotechnics. The deep dewatering treatment system is composed of a magnetization pretreatment apparatus, an automatic powder feeding apparatus, an automatic aqua feeding apparatus, pipelines, valves, sensors, sludge metering pumps, reagent metering pumps, sludge pumps, a vacuum manometer, a plate-and-frame filter press and a filtrate collector, wherein the magnetization pretreatment apparatus can save the feeding amount of reagents and reduce cost for the reagents, and the sensors, the automatic powder feeding apparatus and the automatic aqua feeding apparatus are connected with a control system to realize on-line monitoring of data and automatic regulation and control of reagent feeding, thereby greatly improving work efficiency. Deep dewatering of sludge is realized by cyclically treating sludge to allow sludge to have an optimal pretreatment effect. The deep dewatering treatment system has the advantages of reasonable design, a simple structure and convenient operation and can realize deep dewatering of sludge and low energy consumption and cost in modification and dewatering of sludge under the condition of cooperative pretreatment by multiple factors like magnetization and the reagents.