The invention discloses a bicolor dual-view field infrared imaging optical system. The bicolor dual-view field infrared imaging optical system is characterized by consisting of five lenses including a front fixing lens set (9), a multifocal lens set (10) and a rear fixing lens set (11), wherein the front fixing lens set consists of two lenses, the multifocal lens set consists of one lens, and therear fixing lens set consists of two lenses. The multifocal lens set can axially move in front of or behind a primary image surface to realize switching between a wide view field and a narrow view field; in the five lenses, lenses with a binary diffraction surface is used as a second surface of a second lens and a second surface of a fourth lens. The bicolor dual-view field infrared imaging optical system has the advantages of simple and compact structure, small system size and less lenses, can simultaneously performing imaging at a medium wave infrared wave band with wavelength of 4-5 microns and a long wave infrared wave band with wavelength of 8-9 microns while implementing functions of searching (a wide view field of 9 degrees* 6.75 degrees) and aiming (a narrow view field of 3 degrees*2.25 degrees). The system design takes account of miniaturization and lightweight requirement of the infrared system and meets the use technology requirement of the infrared system.