The invention relates to a central cooler back-washing device for a dredger, belonging to the technical field of dredging construction. The central cooler back-washing device for the dredger is characterized by consisting of a seawater pump, valves and pipelines, wherein the outlet of the seawater pump communicates with an outboard through valves and a seawater filter; the outlet of the seawater pump is connected with two central coolers in parallel through pipelines and valves; the seawater outlets of the two central coolers are connected with the inlet pipeline of the seawater pump and the outboard through valves; pipelines between the seawater inlets of the two central coolers and the valves are connected with back-washing check valves; and the back-washing check valves communicate with the outboard through pipelines and sea valves. The central cooler back-washing device has the advantages that the structure is simple; cost is low; cost performance is excellent; no additional energy is needed; practicability is high; operation is convenient; controllability is good; the central cooler back-washing device is applicable to back-washing of all plate-cooling heat exchangers, especially the dredger during coastal construction; and the like.