The invention discloses an anti-block ratchet wrench which comprises a wrench body. The wrench body is provided with a first containing space and a second containing space, a drive unit is disposed in the first containing space in a rotary mode, a ratchet device is disposed in the second containing space of the wrench body, the ratchet device comprises a first ratchet block, a second ratchet block and an elastic unit, a reversing switch is pivoted to a control groove and is capable of controlling engagement of the ratchet device and the drive unit, a locating unit is connected to the first ratchet block and the second ratchet block of the ratchet device, the locating unit enables the first ratchet block and the second ratchet block of the ratchet device to keep a distance as large as one restrained tooth number from the nearest two tooth parts of each, and the distance of the restrained tooth number is smaller than the distance of a blocking tooth number. Therefore, the ratchet device is prevented from being blocked.