The monitoring system for coal mine safety is reported precisely which was developed to coordinate primarily environmental monitoring information in mines. The system consists of sensors, transmitters and a processor, and a gas chromatograph consists of two columns and two detectors to measure simultaneously several main components in mine gas. The transmitter features less electrical noises, and the processor is a commercial minicomputer for scientific calculation. The main program consists of seven independent tasks to give priority to data gathering for every five seconds. The monitoring method for major disaster prediction and early detection is analyzed on the basis of observational data, and air velocity monitoring which is most important among several usual environmental monitoring in mines is discussed on the basis of experimental results. The behavior of methane gas sensor output during post-disaster monitoring is also discussed on the basis of experimental results. 77 refs., 54 figs., 10 tabs.