Traditional ship flat board measurement uses a leather tape to measure manually. This method has low accuracy, large errors and relies on the experience of the surveyor. Since the cutting of straight plates is mostly large plates, the contact measurement method cannot be widely used. The use of embedded line laser vision sensors combined with numerical control machine tools to propose a method for measuring flat plates of large ships can solve the above problems. The sheet is scanned by the line laser vision sensor, and the obtained real-time coordinates of the machine tool and the calibration result of the relative relationship between the vision sensor and the machine tool are used to unify the measurement results in the machine tool coordinate system, Through the optimized point cloud boundary contour feature extraction method, the rapid and accurate extraction of the boundary features of the measured board is realized, and the straight line is fitted from the boundary contour points and the size is calculated. Experiments show that the measurement error of this method is less than 0.1mm and the repeatability accuracy is higher than 0.2 mm, which meets the design accuracy requirements.