Abstract: Aiming at the disadvantages of big temperature drift, inaccurate protection and big individual difference during mass production of the traditional protection scheme using audion and stabilivolt tube to carry out protect, we proposed a low-cost design scheme for mine-used circuit voltage protection of intrinsically safe power supply with voltage reference AZ431 and comparator LM339, and analyzed the principle of this protection circuit. The circuit has the advantages of simple reliability, convenient debugging and good production. The test shows that the circuit can recover automatically after the failure and the recovery time can be adjusted.