The invention discloses an overrun clutch. The overrun clutch comprises an operation rod, a first cover plate, a middle rotation block, a second cover plate, an internal-external tooth rotation ratchet wheel and a pawl, wherein a first end of the operation rod is used for bearing exerted loads, the first cover plate is connected to a second end of the operation rod, one surface of the middle rotation block is connected to the first cover plate, the second cover plate is connected to the other surface of the middle rotation block, the internal-external tooth rotation ratchet wheel is coaxial with the middle rotation block, an installation track used for installing balls is formed between external teeth of the internal-external tooth rotation ratchet wheel and internal teeth of the internal-external tooth rotation ratchet wheel, the first cover plate and the second cover plate are installed at the two ends of the balls inside the installation track in a supported mode, a first end of the pawl is connected to the middle rotation block in a rotating mode, and a second end of the pawl is arranged anticlockwise relative to the first end of the pawl and can mesh with the internal teeth of the internal-external tooth rotation ratchet wheel. According to the overrun clutch, force exerted on the internal-external tooth rotation ratchet wheel by the pawl is direct driving force instead of friction force, so that part abrasion is reduced, stress concentration is avoided, and a lever is formed among the pawl, the middle rotation block and the operation rod and can transmit large torque.