The invention discloses a large-view field thin film diffraction achromatism optical system and an infrared light correction method. The large-view field thin film diffraction achromatism optical system comprises a plane thin film diffraction primary mirror, an aberration correction lens set and a filter, wherein the aberration correction lens set is composed of five lenses; a radiation beam of an imaging target passes through the plane thin film diffraction primary mirror and then enters the optical system, the aberration correction lens set corrects a chromatic aberration generated by the plane thin film diffraction primary mirror and other aberrations, and then through the filter, the beam is focuses on an image surface for imaging. The large-view field thin film diffraction achromatism optical system and the infrared light correction method have the advantages of wide spectrum section range, large relative aperture, large view field, good imaging quality, compact structure, small size and light weight and the like, the traditional diffraction optical system design method is broken, and the irreconcilable contradiction between the large aperture and the weight of the existing optical system can be overcome.