The invention relates to a blocking protector for a header. The blocking protector comprises a header transmission shaft, a sprocket and a clutch; the sprocket is mounted on the header transmission shaft; the clutch comprises a left meshing gear ring, a right meshing gear ring, springs and spring holders; the clutch and the sprocket are both disposed in the middle of the header transmission shaft; the left meshing gear ring, the right meshing gear ring and the springs sleeve the header transmission shaft; one end, with meshing teeth, of the left meshing gear ring meshes with one end, with meshing teeth, of the right meshing gear ring; one end, with no meshing teeth, of the left meshing gear ring is fixedly connected with the sprocket into a whole capable of idling on the header transmission shaft; the springs are disposed between one end, with no meshing teeth, of the right meshing gear ring and the spring holders fixed on the header transmission shaft; the center of the right meshing gear ring is provided with a key groove in transmission fit with a key arranged on the header transmission shaft. The blocking protector is simple in structure and needs small space.