Abstract: To meet the need of gas monitoring of coal mine, an intelligent gas monitoring system based on wireless sensor networks was developed. The system uses digital gas sensor to measure gas real-timely, so as to decrease complexity of A/D conversion in normal sensors and improve measuring precision. It also uses wireless sensor networks to overcome limitation of wiring sensor networks and avoid high power of other wireless communication technology. The paper introduced hardware and software design of the system in details and gave test results.