Objects automatic labeling method and system applying the same

An automatic object labeling method includes steps: M continuous image frames are captured at one station of an assembly line. An object detection step is performed which includes selecting a detection image frame that displays an operation including a work piece and a target object from M continuous image frames; and calibrating the position range of the target object in the detection image frame. An Nth retrace image frame is selected from the M consecutive image frames retraced forward from the detection image frame, and a target image of the target object is obtained from the Nth retrace image frame according to the position range. The target image is compared with the M continuous image frames to match at least one other image similar to the target image both are stored as the same labeled data set.