Due to the problems of torsion and swing of worktable in food machinery processing enterprises, errors happen to the docking in the mechanical processing. Therefore, a platform for the production line docking system, based on three-dimensional projection matrix, was designed to proposed to reduce docking error. Firstly, the three-dimensional motion platform of the system adopted a stepping motor controlled by pulse signal to achieve the limit control of machine tool. Secondly, the laser control of the system was realized by controlling the laser switch and the output power of the laser. Thirdly, the displacement measurement technology of Doppler frequency difference was adopted, and the AC front-end was also applicated. The amplifier replaced the conventional DC amplifier to obtain accurate real-time measurement data. Finally, the feature points of the docking area image were extracted by the system software, according to the principle of three-dimensional stereo vision proofreading. When checking the three-dimensional docking image of the machining platform based on the feature points, the minimum value of the docking objective function of the three-dimensional phase projection matrix was solved by Powell method, which realized the high precision docking of the mechanical processing. The results showed that the maximum relative error of mechanical docking was 1.50%, with a high accuracy and a quick performance, and only 18~23 minutes was needed.