The invention provides a two-waveband infrared optical system, belongs to an infrared remote sensing optical system, and solves the problems of limited optical path layout of the conventional map-integrated device and large volume of the entire device. The system comprises a scanning rotating mirror, a two-waveband infrared optical lens, a spectrometer, an infrared focal plane detector and a signal processor, wherein the two-waveband infrared optical lens consists of an infrared window, a beam splitter, a medium wave lens and a long wave lens; the scanning rotating mirror is positioned above the infrared window; an infrared optical fiber transmits infrared light output by the medium wave lens to the spectrometer; the infrared focal plane detector is positioned on an output optical axis of the long wave lens; and output signals of the spectrometer and the infrared focal plane detector are transmitted to the signal processor through a transmission cable. The system has small volume, high integration level, and convenient and flexible use, can realize automatic scanning, identification and track of a target by observing two wavebands of external scenery, and can be effectively applied to military or civil fields of missile infrared guidance, atmospheric pollution, remote measurement of poisonous gas and the like.