Abstract: For problems that instantaneous large current in start of mine-used devices could lead to power supply cutting-off and abnormal start of the devices, the paper introduced design of a kind of soft-start circuit for mine-used intrinsic safety devices which is composed of simple components. It gave principle of the circuit and analyzed performances of soft-start, current limit, delay and under-voltage cutting-off of the circuit. The test result proved validity and reliability of the circuit.