Abstract: The pellet tracking system is an auxiliary measuring system of the pellet internal target equipment. The pellet internal target system, which is often used in hadronic physics experiment, is an internal target with 4π coverage for reaction productions detection. The pellet will interact with the circulating ion beam perpendicularly in the reaction chamber. The precise determination of the reaction vertex is very helpful for the reconstruction of the events with short lived production particles. The pellet tracking system with other controllers can determine the position of reaction vertex very precisely to an order of ten micrometers. The principle of the pellet tracking system was described in this paper, in which the pellet’s position is determined by using the scattering light from pellet. The structure was determined based on the tests before the system was built. The angle between the laser and the camera is 135° and the laser power is 5.5 mW. The frequency of the line scan camera AVIIVA M2 CL is 98.000 8 kHz. The minimum distance between the lens M7528-MP and the object is 285 mm, and at this position the magnification is 0.224.