In order to upgrade the cut-by-length technology of billet to cut-by-weight, a real-time accumulation vision weight method of billet based on linear structured laser was proposed, and its principle, measurement model and weighing process were studied. According to the vision measurement principle of linear structure laser, the current cross section area of billet was measured and calculated by two vision sensors. Meanwhile, the distance between the current cross section and the previous one was acquired by another vision sensor, and the billet weight between two adjacent cross sections was calculated and accumulated. Thus, the billet weight passing the measuring position was monitored real-timely, and the real-time weight-cut control of billet was realized. The experimental system was set up and the weight experiment was carried out with rectangular solid steel. Experimental results show that the relative error of weight is 1‰, which is far less than 8‰ used in present production enterprises. This research provides a theoretical reference for the realization of billet cut-by-weight technology.