Purpose <p>The upgrade project of BEPCII (Beijing Electron-Positron Collider II) has imposed new requirements on the magnet power supply system. These requirements include higher power capacity, enhanced performance, and new functionalities such as synchronization capability among power supplies. In order to fulfill these requirements, a portion of the BEPCII magnet power supplies have been completely redesigned and newly manufactured, whereas the remaining units have been upgraded and retrofitted.</p> Methods <p>The dipole magnet power supplies were completely redesigned and rebuilt due to their insufficient output power for the BEPCII upgrade project requirements. For the corrector magnet power supply upgrade, high precision and synchronous output had to be achieved cost-effectively. Accordingly, three control modes were deployed with the choice depending on the power level of each supply. And new high-precision skew quadrupole magnet power supplies were also fabricated for the upgrade project.</p> Results <p>The new dipole magnet power supply not only features increased maximum output current and voltage, but also demonstrates improved performance in current stability and repeatability. The upgraded corrector power supplies exhibit enhanced current stability, reduced voltage ripple, and have achieved multi-power-supply synchronization capability. The SKQ power supplies met or exceeded all design specifications in testing.</p> Conclusions <p>Through systematic upgrades and modifications, the magnet power supply system now fully meets the operational requirements of BEPCII upgrade project in terms of power capacity, performance, and functionality.</p>