The invention discloses a nadir and limb common optical path integral optical system, relates to the technical field of space optics, and aims to solve the problems that detection information is not complete, and use requirements are hard to met as a conventional spatial atmospheric remote sensing detection has single modes. A nadir and limb imager comprises a front lens group, a panorama annular lens, a relay lens group, narrow-band filters and a CCD detector. For a nadir view field, the panorama annular lens is equivalent to a thick lens; the light beam size of a light beam of the nadir view field is firstly reduced through the front lens group, and then the light beam is imaged on the CCD detector through the panorama annular lens and the relay lens group. For a limb view field, light firstly passes through the panorama annular lens to form a virtual image, and the virtual image formed by the panorama annular lens is amplified by the relay lens group and is imaged to the CCD detector. By adopting the nadir and limb common optical path integral optical system, all-direction detection of nadir 10 degrees and limb 360 degrees, and six wave bands are selected by using six narrow-band filters, so that detection information completeness and inversion accuracy of a trace gas can be improved, and the system is applicable to the field of spaceflight atmospheric remote sensing.