A novel water channel dredging device comprises a shell structure, a pulling structure and a crushing structure. The shell structure comprises a shell and a first through hole, the pulling structure comprises an air cylinder, a pull rod, a lifting frame and a piston, and the crushing structure comprises a connecting shaft, a third filter screen, a positioning frame below the filter screen, a sliding block, a crushing pin and a scraping block. The upper end of the connecting shaft is accommodated in the lifting frame and is in threaded connection with the lifting frame, and the positioning frame penetrates through the left surface and the right surface of the sliding block and is in sliding contact with the sliding block. The upper end of the crushing pin is fixedly connected with the sliding block, and the lower end of the crushing pin is fixedly connected with the scraping block. The air cylinder pulls the pull rod to continuously move up and down, the third filter screen, the positioning frame, the sliding block, the crushing pin and the scraping block periodically rotate accordingly through the lifting frame and the connecting shaft which are in threaded connection, due to the periodic change of rotating directions and rotating speeds, sludge can be crushed, meanwhile, the sliding block moves back and forth on the positioning frame, and the sludge crushing range of the crushing pin can be enlarged.