Abstract: The existing non-intrinsic safety type network interface does not manipulate over-voltage protection and current limiting for input and output signals. Electric spark produced by fault or thermal effects may ignite hazardous gas and cause gas explosion, so it can not be directly applied to intrinsically safe network interface circuit. To solve this problem, the existing non-intrinsic safety network port circuit is improved, and the internet access without a transformer, transformer chip, current-limiting resistor, overvoltage protection is adopted to carry out current-limiting and voltage-limiting protection of input and output signals to meet the requirements of intrinsically safe signal input and output. After testing, the output energy of circuit under normal and fault state meets the requirements of intrinsically safe circuit.