The utility model discloses a waste rock blocking device which comprises a waste rock blocking mechanism arranged on a cable trough of a scraper conveyor, the first end of a first connecting rod of alarge waste rock blocking plate mechanism of the waste rock blocking mechanism is hinged to the cable trough, and the first end of a second connecting rod of the large waste rock blocking plate mechanism is hinged to a large waste rock blocking plate which is vertically arranged and can rotate. The telescopic rod end of a transversely-arranged large gangue blocking plate telescopic oil cylinder ishinged to the second end of the first connecting rod and the second end of the second connecting rod, and the cylinder body end of the large gangue blocking plate telescopic oil cylinder is hinged tothe cable trough. During use, under the action of the large gangue blocking plate telescopic oil cylinder, the first connecting rod and the second connecting rod are driven to act, so that the largegangue blocking plate rotates, the plate face of the large gangue blocking plate is perpendicular to the middle groove, gangue on a large-dip-angle fully mechanized coal mining face can be effectivelyprevented from sliding down, and the safety of workers and equipment on the fully mechanized coal mining face is guaranteed.