The invention discloses a posture and moving track positioning system and method of robot grabbing an online workpiece. The device comprises a camera support, an industrial camera, the tested workpiece, a workpiece conveying belt, a tail end executer, a robot system, a workbench, an image processor and the like. The method comprises the steps that a depth positioning model of a plane point in an absolute coordinate system in the vertical direction, a depth positioning model of a space point in the absolute coordinate system in the vertical direction, an X-axis positioning model of the plane point in the absolute coordinate system in the horizontal direction and an X-axis positioning model of the space point in the absolute coordinate system in the horizontal direction are established, three-dimensional coordinates of imaging points in all the cameras can be solved through combination of the priori knowledge of the workpiece, accordingly, and a robot can be guided to adopt the accurate tail end executer posture and movement track to intelligently grab the workpiece accurately. The posture and moving track positioning system and method have the advantages that the grabbing precision is high, the structure is simple, and cost is low.