Farmland irrigation channel dredger with automatic dredging device

The invention discloses a farmland irrigation channel dredger with an automatic dredging device. A box is included. The box is provided with a first work cavity with a forward opening. A throwing device is fixedly arranged on the inner wall of the rear side of the first work cavity. Side wall adjusting devices symmetric relative to the throwing device and moving devices symmetric relative to the throwing device are arranged on the left side and the right side of the box. A shearing device is arranged in each side wall adjusting device. A pulverizing device is arranged in the throwing device. The farmland irrigation channel dredger is placed in a channel, the bottom of the machine can smash sludge below the channel, meanwhile, the two sides can be laid on the channel wall, and weeds on thechannel wall can be pulverized; the angle of the two sides can be constantly adjusted according to the channel angle, and accordingly maximum attachment is achieved; and the machine can throw sludge and sundries to the outer