The invention discloses a three-dimensional part calibration system and method during laser processing. The system comprises a mechanical arm, a mechanical arm tail end flange, a galvanometer system,a paraxial mounting plate, an industrial camera, a part to be machined and an etching trial target. The galvanometer system is mounted on the mechanical arm through the mechanical arm tail end flange. The galvanometer system and the industrial camera are mounted together through the paraxial mounting plate in a paraxial manner. The part to be machined and the etching trial target are fixed to a work table top and located on the lower portion of the industrial camera. By means of the calibration system and method, strict mechanical clamping locating is not needed when the industrial camera anda galvanometer are mounted; the problem that part position finding during laser three-dimensional part machining is difficult is solved; and the base surface of the three-dimensional part and the work table top are simply placed in a coinciding manner, the mechanical arm guides the industrial camera to achieve part position finding automatically, efficiency is high, and precision is guaranteed.