The utility model relates to a PDC drill bit suitable for mud stone stratum, including drill bit body and a plurality of wing, a plurality of wings along the tip of fixture sliding seat such as circumferencial direction at the drill bit body, one side of wing is equipped with a plurality of front -seat cutting teeths side by side, and the top surface of wing is equipped with a plurality of back rows cutting teeth, the height that highly is higher than front -seat cutting teeth of back row cutting teeth, the shape of back row cutting teeth is the positive pentagonal prism body, and it rotates the top surface of connecting at the wing, and the rotation axis of back row cutting teeth is its axial direction line, and the rotation axis is parallel with the top surface of wing. The utility model discloses the back row cutting teeth of PDC drill bit is the positive pentagonal prism body, and the high high 2mm~3mm of the front -seat cutting teeth of high ratio of back row cutting teeth. Consequently, the back row cutting teeth at first marks the multichannel line that breaks on boring the rock, reduces the intensity of rock, reduces the resistance on front -seat cutting teeth cutting stratum. Simultaneously, can rotate after the back row tooth is contacting the stratum, avoid the single face to strike rock, extension bit life.