The invention relates to a special joint type grinding wheel. The grinding wheel is formed by four sector joint grinding wheels. Each sector joint grinding wheel is composed of an inner sector inner outline, an outer sector outer outline and side lines connecting the sector inner outline with the sector outer outline, wherein a center locating shaft hole is formed in the sector inner outline, an outward joint convex groove is arranged on the side line on one side, and an inward joint concave groove is arranged on the corresponding side line on the other side. Corresponding mounting holes are formed in the joint convex grooves and the joint concave grooves. Concave grooves are formed in the sector outer outlines, grinding layers extending outwards are jointed in the concave grooves, and thegrinding layers and the sector joint grinding wheels are fixed through bolts. The special joint type grinding wheel has the advantages that the outward convex grooves and the inward concave grooves are correspondingly arranged on the side lines of the sector joint grinding wheels, and mounting is facilitated; and the grinding layers are further fixed to the sector outer outlines of the sector joint grinding wheels, during use, the sector joint grinding wheels can be overall replaced, only the grinding layers can be replaced, and cost is saved.