Abstract: The paper put forward a design scheme of portable methane annunciator based on infrared optics（principle） and introduced design of hardware circuit and software, structure of optics gas chamber and outline design of the instrument and calibration technology in details.The annunciator realizes real-time detection of CH4 by use of infrared source,integrated pyroelectric detector with high-precision interference filters,single-beam dual-wave length technology and gas chamber with gold-plated membrane,which has some advantages such as not-easy ageing,rapid response,high sensitivity,stabilization and strong anti-jamming capability.