Motor-driven reducing PDC (Polycrystalline Diamond Compact) drill bit

A PDC drill bit with variable diameter driven by a motor comprises a drill bit body, a barrel, a male connector, a motor driving unit and a movable blade, a wedge-shaped T-shaped groove is formed in the inner side of the movable blade, the wedge-shaped T-shaped groove enters a cavity formed after the drill bit body, the barrel and the male connector are communicated through a blade groove, and a wedge-shaped T-shaped block sliding along the wedge shape of the wedge-shaped T-shaped groove is arranged in the wedge-shaped T-shaped groove. And the wedge-shaped T-shaped block is fixedly connected with the guide head of the motor driving unit and axially moves along with the guide head of the motor driving unit. The motor driving unit is arranged in the drill bit, the driven wedge-shaped T-shaped block slides in the wedge-shaped T-shaped groove formed in the inner side of the movable blade in the wedge shape of the wedge-shaped T-shaped block, meanwhile, the movable blade is driven to move in the radial direction o