To provide a deposition preventing structure and a deposition preventing system and method that can effectively prevent deposition of an underwater deposit in a sedimentation area of a reservoir by efficiently accumulating the underwater deposit such as sand upstream of the sedimentation area of the reservoir such as a dam and removing the accumulated deposit.

The deposition preventing structure 10 includes a screen body 11 installed extending from the water bottom G close to the water surface S to face the flow direction A of water on upstream side of the sedimentation area 3 of the reservoir 2.