The invention relates to the technical field of water conservancy equipment, in particular to a water conservancy river way trash holding and flood preventing device. Fixed frames, a fence, baffles, strip-shaped through holes, an upper slide rail, a lower slide rail, a movable scraper blade, a driving device, trash holding plates, a first containing cavity, a folding baffle, a first control box, arotating shaft, a rotating wheel, a second storing cavity, a second control box and a limiting groove are included; the two fixed frames are arranged, and the fence and the baffles are arranged between the two fixed frames; the baffles are provided with the strip-shaped through holes; the front side walls of the top end and the bottom end of the fence are provided with the upper slide rail and the lower slide rail correspondingly; the movable scraper blade is installed between the upper slide rail and the lower slide rail in a sliding manner; the driving device is arranged at the top end of the upper slide rail; and the outer side walls of the two fixed frames are each provided with the corresponding trash holding plate. The water conservancy river way trash holding and flood preventing device is simple in structure and convenient to install, has a trash holding and fold preventing function, trash can be subjected to concentrated collecting treatment, and manpower clearing is facilitated; and meanwhile, a flow limiting flood discharge effect is achieved, a river bottom sludge stirring structure is achieved, and normal passing of water flow is guaranteed.