The experimental Cooler Storage Ring (CSRe) of the Heavy Ion Research Facility in Lanzhou (HIRFL) is an experimental platform for nuclear mass measurement. The particle beam required for the experiment moves in a vacuum tube under the constraint of a magnetic field. The magnet power supply provides excitation current to the magnet load. The current stability of the accelerator power supply is directly related to the magnetic field. In particular, improving the stability of the magnetic field of the dipole magnet is of great significance for obtaining good beam quality and better carrying out physical experiments. In order to obtain a better magnetic field environment, this paper built a measuring system for the experimental ring dipole magnet power supply, analyzed the current, cooling water temperature and other key factors affecting the output current, and proposed a hysteresis control method to further improve the stability of the power supply. By improving the existing power supply of the dipole magnet, the stability of the output current is improved from 50 ppm to 26 ppm for a long term.