The invention discloses a torque output tool and its one-way torque transmission mechanism, which comprises: a casing, a motor and a transmission assembly, the motor and the transmission assembly are arranged in the casing, the transmission assembly includes a one-way torque transmission mechanism, and the one-way torque transmission mechanism Including: main shaft, driving part, lock sleeve, lock core, lock piece, etc., the lock sleeve includes a lock ring, the lock core includes a cylinder, and the inner wall of the lock ring includes at least two sections that can be locked or loosened with the outer wall of the lock cylinder cylinder The limiting wall surface of the locking part, the locking part is arranged between the locking ring and the cylinder, under the action of centrifugal force, when the driving part is driven to the main shaft, it only contacts the locking sleeve stably without unnecessary impact and friction , improve the efficiency of torque transmission, and reduce the heat generated by this mechanism, so as to reduce the adverse effects of temperature rise on tool reliability.