An overvoltage and undervoltage protection circuit for low-voltage systems is designed. The output voltage threshold accuracy is improved through a circuit structure similar to a bandgap reference, low-voltage conditions are achieved by reducing the use of diodes, and a certain hysteresis is designed in the undervoltage protection threshold voltage of the circuit to prevent the system repeatedly turning off near the threshold, and the functional correctness of the circuit is verified in the simulation of the low-voltage power management system application. The circuit is designed and simulated using SMIC 0.18 μm standard CMOS process and Cadence software. The results show that when the power supply voltage rises within the temperature range of -40~85 ℃, the circuit starts to work normally and the voltage threshold is 2.431~2.50 V, the threshold accuracy is 3.2%, the overvoltage protection threshold is 4.931 ~5.22 V, the accuracy is 5.7%, when the power supply voltage drops, the undervoltage detection threshold is 1.58~1.663 V, the accuracy is 4.9%. The system application simulation results show that when the power supply voltage exceeds the normal operating voltage threshold of the system, the over-voltage and under-voltage protection circuit will control the system to enter the shutdown mode and realize the protection function.