In the process of three-dimensional scanning and imaging of objects on the conveyor belt, the convenience and accuracy of the displacement calibration method have a very important impact on the final imaging accuracy and efficiency, but the traditional displacement calibration method requires knowing the movement speed of the displacement platform and conveyor belt or strictly controlling the precise displacement between the calibration plates in the two calibration pictures, which makes the calibration process more complicated. A displacement calibration method of linear structured light 3D scanning and imaging system specially used for object measurement on conveyor belts is proposed. This calibration method only needs to collect a series of displacement calibration pictures of the calibration plate moving with the conveyor belt, extract two pictures with a frame interval greater than 1 and record the corresponding number of frames to calibrate the single frame displacement. The basic principle and implementation method of the calibration method are introduced, the line scan monocular imaging system is built, and the double-step precision block is reconstructed in three dimensions. The experimental results show that the method is simple in principle, convenient in operation, faster in measurement speed and simple in operation, and the reconstruction error is less than 0.3mm. It is suitable for real-time three-dimensional measurement in various fields where the conveyor belt is the main means of transportation.