The invention discloses a dust falling device for a mine downhole fully-mechanized coal mining face shifting frame falling coal fog gun. The dust falling device includes a negative-pressure generator,an atomizing mechanism and a dust suction tube, the negative-pressure generator is fixed to the upper end of a gangue sliding groove, the gun muzzle end of the negative-pressure generator directly faces the coal wall, an airflow expansion cavity is formed in the side wall of the negative-pressure generator, an air inlet is formed in the corresponding outer side wall of the air flow expansion cavity, an annular nozzle is arranged on the corresponding inner wall, a dust suction mouth is formed in the side wall of the end, away from the gun muzzle, of the negative-pressure generator to be connected with the dust suction tube, the free end of the dust suction tube is located in the gangue sliding groove, and compressed air is ejected from the annular nozzle and forms a negative -pressure cavity in the rear end to suck dust in the gangue sliding groove; and the atomizing mechanism includes a high-pressure water pipe extending into the negative-pressure generator, an atomizing spraying headinstalled at the end of the high-pressure water pipe and a diffusion plate located on the front part of the atomizing spraying head, atomized water ejected by the atomizing spraying head touches thediffusion plate and then bounces and diffuses and is mixed with sucked dust to form dust-containing water mists to eject to the gun muzzle, and high-efficiency dust falling is achieved.