The invention discloses a DMD spectral dimension coded dual optical path Offner light splitting/combining medium-wave infrared spectral imaging device, and the device belongs to the technical field ofinfrared spectral imaging. Devices in the prior art cannot satisfy the demands of all-day work. The device provided by the invention is characterized in that a back focal plane of a medium-wave infrared achromatic variable-focus object lens group coincides with an initial object plane of a dual optical path Offner light splitting/combining system; the dual optical path Offner light splitting/combining system consists of a concave spherical reflecting mirror and a convex spherical reflection grating, the concave spherical reflecting mirror and the convex spherical reflection grating have the same curvature center, and the ratio of curvature radius is 2:1; the medium-wave infrared achromatic variable-focus object lens group and the medium-wave infrared DMD are symmetric with respect to theconvex spherical reflection grating, and the medium-wave infrared DMD is located at an image plane of the dual optical path Offner light splitting/combining system; a folding mirror is located on thesecondary imaging optical path of the dual optical path Offner light splitting/combining system, and a refrigeration type medium-wave infrared detector is located on the reflected optical path of thefolding mirror; and the refrigeration type medium-wave infrared detector is connected to an image acquisition card, and a computer is separately connected to the image acquisition card and the medium-wave infrared DMD.