The invention discloses a high-efficiency coarse grain wet type permanent preselecting and waste-throwing magnet separator. A groove body (7) employs a co-flow structure; a layer of ceramic wear resistant material adheres to the surface of a cylindrical shell (8), wherein the ceramic wear resistant material layer is formed by splicing small ceramic sheets according to rows and columns on the 360-degree circumferential surface of the cylindrical shell; backwashing water pipes are added on the bottom of the groove body (7); a reciprocating type feeding device is disposed inside a feeding box (5); the reciprocating type feeding device is composed of a material-block plate (11) and a feeding chute (11'); a frequency conversion timing motor is adopted in a transmission device, thus enabling the rotating speed regulation of the cylindrical shell to range from 20 r/min to 40 r/min and the linear velocity from 1.1 m/s to 2.2 m/s. The magnetic separator provided by the invention has advantages of good cylindrical wear-resistant performance, long equipment service life, material nonblocking capacity for the groove body and high sorting efficiency, and is used to process materials with the granularity being 0-20 mm, especially used for the wet type preselecting and waste-throwing of magnetite ore with the granularity being 0-16 mm.