Abstract: The key step in billet flame cutting is to preheat the billet edge, i.e., the preheat point position. The billet is transported in such a way that the edge position is laterally shifted due to the movement, causing the flame cutting preheat point position to deviate from the set value and leading to cutting failure. A method for detecting the edge and preheat point position of billet based on temperature field measurement was proposed, and a detection device was installed in the front of the flame cutting equipment on the conveying track, and the measured billet temperature field information combined with image processing algorithm were used to detect the billet edge position, and the preheat point position of flame cutting was calculated according to the cutting mode of the billet, so as to provide a key technical guarantee for the smooth flame cutting of billet. The field test shows that the detection error of the method is within 1 mm, which can meet the requirements of flame cutting production process and realize the fully automatic operation of billet flame cutting.