The invention relates to a DMD spatial dimension coding symmetric Offner dispersion medium wave infrared spectral imaging device, and belongs to the technical field of infrared spectral imaging. The prior art has the disadvantages that the prior art cannot satisfy the demand for all-weather spectral imaging; the spatial resolution and the spectral resolution are low; the adopted microlens array process is complicated and difficult to process; and the adopted planar grating may cause spectral line bending and color distortion problems. The DMD spatial dimension coding symmetric Offner dispersion medium wave infrared spectral imaging device is characterized in that a working plane of a medium wave infrared DMD is located at an image plane of a medium wave infrared achromatic varifocal objective set; an object plane of a symmetric Offner dispersion system coincides with the image plane of the medium wave infrared achromatic varifocal objective set; a refrigeration medium wave infrared detector is arranged on an emitting optical path of the symmetric Offner dispersion system; and a photosensitive surface of the refrigeration medium wave infrared detector is located at the image plane of the symmetric Offner dispersion system; in the symmetric Offner dispersion system, a spherical reflector and a spherical reflection grating have the same curvature center; and the refrigeration medium wave infrared detector is connected with an image acquisition card, and the image acquisition card, a computer and the medium wave infrared DMD are sequentially connected.