The utility model discloses a double -nut adjusting device, including fixed subassembly and driving medium, fixed subassembly includes mounting and ratchet, the first end of mounting is used for fixed fastening nut, the second end of mounting is equipped with compared with the prior art, the driving medium is worn to establish ratchet's ratchet, just the driving medium with ratchet's ratchet transmission is connected, the one end of driving medium is used for rotating locknut, the rotation direction of ratchet be used for with locknut to unscrew the direction unanimous. When locknut was unscrewed to the driving medium, fastening nut can not rotate along with locknut's rotation under the effect of ratchet's unidirectional rotating, can play the effect of unscrewing locknut in fixed fastening nut, compares in traditional a plurality of instrument compounding practices that utilize above -mentioned double -nut adjusting device convenient operation.