The invention discloses a three-dimensional machine vision based intelligent mechanical arm system and a control method thereof. The control method is characterized in that an object is detected by alaser distance measuring module; after the object is detected, the laser distance measuring module separately triggers a projector, a camera and a camera head, so that the projector, the camera and the camera head co-act to acquire three-dimensional information, which comprises height information, length information, width information and distance information from the center of the object to an origin of coordinates of the mechanical arm, of the object, and the arrival time needed for transmitting the object to a grabbing region from a first information obtaining region is obtained by calculating; and a mechanical arm controller automatically regulates a grabbing position of the mechanical arm according to objects of different specification dimensions, which correspond to the three-dimensional information, and integrates the arrival time of the object, so that intelligent grabbing for the objects of different specifications can be realized.