Abstract: To meet the requirement of safety production for petroleum and natural gas well site, a detailed description is made about the design scheme and the software & hardware design process of a H₂S monitoring system in this paper. Mature microcontroller technology and virtual instrument technology was used in the monitoring system. The mixed signal processor MSP430F149 was used as a field control device. Through the expanded peripheral signal regulate circuit, flash data storage, RS485 interface chip and the corresponding H₂S monitoring probe, then transmitting the received data to the host computer, multiple H₂S concentration real-time monitoring and alarm function were achieved in well site. The research is of practical significance in promoting safety guarantee of petroleum and natural gas production fields.