Abstract: Aiming at the widely used Buck DC-DC power management system, a negative feedback loop for Buck DC-DC power management chip reference circuit is designed in this paper, considering the influence of the voltage accuracy generated by the bandgap reference source on the system output.Based on the analysis of the traditional BJT-based voltage reference source, this paper selects Huahong 0.18μm BCD process and performs simulation in the temperature range of -40℃ to 100℃. When the input voltage is 5 V, the temperature coefficient of the reference source is4.9×10^－6ppm/℃, and power supply rejection ratio(PSRR) is -65.8 dB@dc, -40.2 dB@1.5 MHz, all of which show good performance.