:A method for three-dimensional scanning of large-size workpieces based on monocular line structure light is proposed.Visual sensor mathematical model and polynomial model were established by introducing the light plane of the line structure,and the camera and the light plane were calibrated by using the high-precision manual translation stage to control the movement of the parallel line target in six fixed positions to improve the accuracy and accuracy of the calibration.At the same time,accurate measurement of the workpiece part of the effective area,reducing the amount of program operations.The scanning method can directly construct the measurement coordinate system of the sensor,the process is simple and the speed is fast.Through scanning tests on large-size aluminum alloy castings,a suitable scanning speed v=1.25 mm/s was selected,and the efficiency of industrial application was improved under the premise of satisfying the accuracy.The experimental results show that this method can effectively and accurately reconstruct the surface of the object with an average error of less than 0.1 mm and high accuracy.