The present invention relates to a PDC drill bit. The present invention resolves the following defects of the prior PDC drill bits: the requirement on high drilling speed can hardly be met, the round trip is frequent, and the operation cost is high. Long blades (2) and short blades (3) are arranged in pair and staggerly distributed along the radial direction of the drill bit; blade body grooves (8) are arranged at positions at which a steel body (14) axially corresponds to the long blades (2); fixture blocks (12) are assembled in fixture block sockets (11) positioned on the steel body (14) and the long blades (2); springs (12) are assembled in the fixture block sockets (11); a limit socket (10) which is parallel to the fixture block socket (11) is arranged on the inner side of the blade body of each long blade (2); and when the blade bodies of the long blades (2) enter into the blade body grooves (8), the fixture blocks (12) enter into the limit sockets (10). The PDC drill bit has thefollowing advantages: because the blades can be replaced according to different stratum-drilling requirements, the PDC drill bit can realize high-speed soft stratum drilling, the round trip does not need to be carried out when the drill bit needs to be replaced in order to drill a hard stratum, as a result, time is saved, and the operation cost is reduced.