A multiband imaging technology based on large aperture spatial heterodyne imaging spectroscopy (LASHIS) is proposed in this paper. It retains the advantages of high spectral resolution, high stability and high detection sensitivity of LASHIS. In addition, by using the multistage diffraction gratings, several spectral bands can be detected simultaneously in this system, thus the spectral range is broadened. The basic principle of this multiband imaging technology based on LASHIS is described. The difference between optical path differences produced by the Sagnac lateral shearing interferometer and the parallel gratings is calculated. The mathematical expressions, the interferogram calculation procedures, and the spectrum reconstruction method are presented. As a pair of multistage diffraction gratings is introduced into the Sagnac interferometer, the rays of different diffraction orders corresponding to different spectral bands are mixed together in the interferometer. The spectral bands should be separated before they are imaged on the detector. Two separation methods are proposed:introducing a filter array in front of the detector and introducing dichroic mirrors to assign different spectral bands to different detectors. Finally, a design example is given and an optical model is setup in ZEMAX. In this example, a pair of parallel echelon gratings with 316 lines/mm is introduced into the Sagnac interferometer. Two dichroic mirrors and three detectors are used to separate and detect three spectral bands simultaneously. The three spectral ranges are from 529.2 nm to 532.96 nm, from 588 nm to 592.18 nm, and from 661.5 nm to 666.20 nm. The average spectral resolutions are 0.015 nm, 0.016 nm, and 0.018 nm respectively. Two kinds of sources are analyzed:one is a sodium lamp with two emission peaks at 589 nm and 589.6 nm, and the other is a source with three monochromatic wavelengths at 530 nm, 589 nm, and 662 nm. The interferograms of these two sources traced in the optical model are consistent with the theoretical results. The recovered spectra show good agreement with the input spectra. These verified the correctness of the principle and the spectrum reconstruction method. The multiband imaging technology based on LASHIS with the advantages of high spectral resolution, high detection sensitivity, and multiband detection capability, is especially suitable for multiband hyperspectral highstability and high-sensitivity detection, such as the detection of greenhouse gases.