The invention discloses a feed crushing device. The feed crushing device comprises a rack, wherein a crushing conveying tube is arranged on the rack; a grinding hopper is fixedly arranged in a material receiving box; a grinding mechanism is rotatably connected into the grinding hopper; a plurality of filter holes are formed in the bottom wall of the grinding hopper; the top of the grinding hopperis communicated with a negative-pressure mechanism; the crushing conveying tube is rotatably connected with a first negative-pressure blade, a circular disc and a positive-pressure blade; crushing cutters are uniformly distributed in the peripheral direction of the circular disc; the negative-pressure mechanism comprises a negative-pressure tube; a second negative-pressure blade is rotatably connected into the negative-pressure tube; a filter screen covers the second negative-pressure blade; one side of the negative-pressure tube is communicated with a collecting tube; the negative-pressure tube is communicated with an air outlet tube; a plurality of branch tubes are communicated with the air outlet tube; ends, away from the air outlet tube, of the branch tubes are communicated with the grinding hopper; and the branch tubes are positioned on the bottom wall of the grinding hopper. Compared with the prior art, the feed crushing device can perform three-time crushing on feed, and improves preliminary crushing efficiency of feed; and an air aspirator pump does not need to arrange, and the second negative-pressure blade only needs to link by a rotary shaft, so that the cost of the whole device is reduced.