Space-based multi-model differential optical absorption hyperspectral imager is a new type space atmospheric sounder. It requires the multi-model sounding functions including nadir, limb and sun occultation. It chiefly sounds the trace gases such as SO2, NO2 and so on. A new method of multi-model sounding with high spectral resolution is proposed. The method uses two-scanning mirrors to switch differential sounding model, double-spectrometers to reduce the spectral stray light, and dichroic filter to divide working waveband into three channels. An optical system of multi-model differential optical absorption hyperspectral imager is designed. The instantaneous field of view is 1.8°×0.04°. The F number of the system is 2. The working waveband is 250~500 nm, which is divided into three channels, the first one is 250~310 nm, the second one is 300~410 nm, and the last one is 400~500 nm. Optimization design and analysis are performed by ZEMAX-EE software. The spectral resolution is 0.12 nm in the waveband of 250~310 nm, which satisfies the requirement specification of no more than 0.4 nm. The spectral resolutions are 0.25 nm and 0.23 nm in the waveband of 300~410 nm and 400~500 nm, respectively, which satisfy the specification requirement of no more than 0.6 nm. The modulation transfer function (MTF) of multi-model differential optical absorption hyperspectral imager is more than 0.98 at characteristic frequency of 0.25 lp/mm in the spatial dimension. The design results satisfy the requirements of multi-model differential optical absorption hyperspectral atmospheric sounding.