The utility model discloses a filth cutting mill under water for hydraulic and hydroelectric engineering, including crossbeam, crushing blade, frame main part and first live -rollers, the crossbeam is installed on the top of frame main part, and the intermediate position department on crossbeam top installs first motor, the second live -rollers is close to the one end of second motor and installs second from driving wheel, and the second passes through the second belt from the driving wheel and is connected with the second action wheel. The utility model discloses an install first live -rollers and second live -rollers, and all evenly install the winding pole on first live -rollers and second live -rollers, make and be convenient for the pasture and water of winding on the trash rack strip, the transmission of filth such as branch and rattan is smashed to smashing blade department, make and be convenient for directly smash under water the cutting filth, it has not only solved the problem that the stifled plug flow of filth said to make, and the salvage of filth has been avoided, the transportation, settle and bury the scheduling problem, a large amount of artifical labours saves, and convenient use.