Poisson line technique is a method of generating a straight line by diffraction for high precision alignment，which can keep the center of Poisson spot in this line at long distances (several tens or hundreds of meters). Numerical simulation and experimental demonstration are proposed to research this technique. The intensity of the line increases asymptotically to the incident intensity as distance from the disk increases. The diameter of the line increases as the distances from the disk increases. Whereas it decreases as the diameter of the disks increases. The direction of the line is parallel to laser beam and propagates through the center of the disk，which is sensitive to center excursion and insensitive to the incline of the disk. Poisson line is sensitive to 10 μm excursion in simulation. And Poisson line technique can adjust 50 μm center excursion at long distance in experimental demonstration.