The invention discloses a thread machining blade which comprises a blade body. The blade body is provided with a blade center hole and cutting edge parts. Each cutting edge part is defined by a front blade surface, a cutting edge angle arc surface and two cutting edge angle side surfaces in an enclosed mode, wherein the two cutting edge angle side surfaces intersect with the front blade surface to form two side cutting edges, the included angle between the two side cutting edges is a cutting edge angle, the front blade surface is connected with the upper surface of the blade body through a connecting curved surface, the front blade surface is provided with a chip guiding groove which is arranged in a symmetric mode relative to the angular bisector N of the cutting edge angle, a spherical chip breaking boss higher than the front blade surface is formed in an outward protruding mode from the inside of the chip guiding groove, a triangular chip breaking boss is formed by extending from the connecting curved surface towards the inside of the chip guiding groove, and the triangular chip breaking boss is connected with the chip guiding groove in a circular arc transition mode. The thread machining blade has the advantages that machining is easy and fast, chips are low in friction in the flowing process, the degree of finish of a workpiece thread is high, the blade is high in strength, machining efficiency can be effectively improved, and production cost is lowered.