Abstract: A kind of gas detector with light interference based on single-chip microcomputer was designed, which took AT89C2051 as center of control and processing.By use of arithmetics such as digital filtering,numerical value lookup,linearization processing etc.,and based on the principle of light inter-ference and optoelectronic switching,the detector realized accurate detection for gas concentration of coal mine,digital display and overrun warning.It has characteristics of simple use,high reliability.