The invention discloses a supporting roller used for a wet type descaling mill. The supporting roller comprises shaft head bearings which are positioned at the two ends of a supporting roller, and a plurality of back lining bearings which are positioned between the shaft end bearings, wherein the outer side end surfaces, away from the back lining bearings, of the shaft head bearings are equipped with non-contact type sealing structures which have water resistance and are used for preventing water and slag scrap from entering the shaft head bearings through the outer side end surfaces of the shaft head bearings; and waterproof retaining rings are arranged between the back lining bearings and between the back lining bearings and the shaft head bearings, and are used for preventing water andslag scrap from entering the shaft head bearings and the back lining bearings through positions between the back lining bearings and between the back lining bearings and the shaft head bearings. The supporting roller prevents water and slag scrap from entering the shaft head bearings and the back lining bearings of the supporting roller, so that a great deal of water is prevented from entering theshaft head bearings and the back lining bearings to cause supporting roller stalling; and scale slag scrap is prevented from entering the shaft head bearings and the back lining bearings to cause bearing blocking, so that the service life of the supporting roller of the descaling mill is greatly prolonged.