The invention discloses a gear impact fatigue detection device. The gear impact fatigue detection device comprises a workbench, two groups of mounting brackets are fixedly arranged on the workbench, and a driving threaded rod is movably provided with a test gear; an output end of a driving motor is fixedly provided with a rotating shaft, a first connecting rod is fixedly arranged on the rotating shaft through penetration; one end of a connection shaft, far away from a stop dog, is fixed on an impact block; and the impact gear is fixedly arranged at a center of an extension plate; an external side of the rotating shaft is provided with a ring bearing, the ring bearing is movably arranged at the center of a driving gear, and adjusting nuts is arranged at two sides for adjusting a single-tooth gear. The invention provides the gear impact fatigue detection device, in usage, test gear position of he test gear can be automatically and intermittently adjusted, impact times can be counted accurately, reciprocating operation impact of the impact gear can be realized through structures, a motor is free from working intermittently, and thus, the motor is protected effectively, so the gear impact fatigue detection device is very worth being generalized.