Method and system for automatically determining positioning line in detection image

The invention relates to a method and system for automatically determining a positioning line in a detection image. The method comprises the obtaining step of obtaining a three-dimensional model which is in best fit with an object to be scanned and the determining step of projecting the positioning line in the best-fit three-dimensional model to the detection image of the object to be scanned, and therefore obtaining the best positioning line. The system comprises obtaining equipment used for obtaining the three-dimensional model which is in best fit with the object to be scanned and determining equipment used for projecting the positioning line in the best-fit three-dimensional model to the detection image of the object to be scanned, and therefore the best positioning line is obtained.