Abstract: In order to accurately measure the volume of methane gas concentration, we adopted the parallel infrared illuminant, IRL715EN-PR, to design an infrared methane gas detection system . The whole detection system consisted of hardware circuit and software system. We put forward and implemented a new algorithm about signal processing. At the same time, a feeding dog in interrupt service routine (ISR)program was designed so as to greatly extend the watchdog timer reset time. Using Matlab for data fitting, we achieved a function of concentration and voltage of the system. Experiments show that the volume concentration is in the range from 0% to 4%, the greatest relative error of the system is less than 1%.