The invention discloses a blade used for cemented carbide roller rib engraving processing. A relief angle A2 of a side blade is larger than or equal to 7 degrees and less than or equal to 9 degrees. A back cutting face of a major cutting edge is composed of a first major flank, a second minor flank and a third minor flank in succession, and relief angles of them are presented as A1, B and C respectively in order, wherein A1 is larger than or equal to 7 degrees and less than or equal to 11 degrees, B is larger than or equal to 28 degrees and less than or equal to 32 degrees, and C is larger than or equal to 53 degrees and less than or equal to 63 degrees. Relations of height K of the first major flank, height G of the second minor flank and blade thickness H are that K is larger than or equal to 40% of H and less than or equal to 58% of H, and G is larger than or equal to 25% of H and less than or equal to 37% of H. A relation of the blade thickness H and a blade cross section diameterD is that H is larger than or equal to 60% of D and less than or equal to 85% of D. A composite structure of a cemented carbide substrate and PCD layer are employed, binder phase in the cemented carbide substrate is pure cobalt, and weight percentage Co of the pure cobalt is larger than or equal to 20% and less than or equal to 30%. According to the invention, a problem of blade broken in a rib engraving process of processing a two-dimensional ribbed steel bar with cemented carbide roller is solved, a surface roughness requirement of rib type is satisfied, blade broken problem is further solved, and processing efficiency is raised.