The utility model discloses a nut locking mechanism of a stretching-drawing machine. The nut locking mechanism comprises a stretching-drawing nut, a first gear, a second gear, a third gear, a first rotating shaft, a retainer, a second rotating shaft, a third rotating shaft and a handle. The stretching-drawing nut is sleeved with the first gear, and the inner hole structure of the first gear is matched with the stretching-drawing nut. The second gear is a stepped gear formed by a driving gear and a driven gear, and both the driving gear and the driven gear are arranged on the second rotating shaft. The third gear is arranged on the third rotating shaft, and the handle is arranged on the third gear. The first gear is meshed with the driven gear, and the third gear is meshed with the driving gear. At least three through holes are formed in the retainer, and the first rotating shaft, the second rotating shaft and the third rotating shaft are arranged in the three through holes respectively. The nut locking mechanism is reasonable in structure and convenient and fast to operate. By the adoption of the nut locking mechanism, a worker can lock the stretching-drawing nut without putting the hand into a stretching-drawing sleeve, so the production efficiency can be improved greatly and accidents can be reduced.