The invention relates to an anti-settling device for a flotation machine with a U-shaped groove. An annular air pipe arranged along a horizontal direction communicates onto a main air supply pipelineof an air supply system of the flotation machine with U-shaped groove; at least four vertical pipes communicate onto the annular air pipe and are distributed along the periphery of the U-shaped groove; the lower ends of the vertical pipes extend to the bottom parts of four corners of the U-shaped groove; and sleeves are sleeved on the peripheries of the vertical pipes. The anti-settling device forthe flotation machine with the U-shaped groove provided by the invention has the advantages that an original air supply system is used, so that the problems of coarse particle settling and depositingare effectively solved, the defect that central air supply and stirring in an original flotation machine cannot effectively improve four-corner coarse particle ore-accumulation is overcome, a flotation effect is improved, and an adaptive capacity of the flotation machine with the U-shaped groove on particle size is improved.