One coaxial and off-axial hybrid three-mirror optical system is designed, by combining a coaxial threemirror system and an off-axial three-mirror system. A 10×0.1° field of view (FOV) is achieved by the F/7.3 coaxial system with spectral coverages of 0.38~0.78 μm and 1.2~1.7 μm. A 2°×0.1° FOV is achieved by the F/18.9 off-axial system with spectral coverage of 0.38~0.78 μm. The above two systems have the same focal length of 14 m, and the simultaneously performing push-broom imaging ability. They both have a middle image plane and a real exit pupil which can supress stray light easily. After an optimization, near diffraction-limited performance can be obtained over all the FOVs and the spectral ranges. A minimum modulation transfer function (MTF), higher than 0.41 at Nyquist frequency, is acquired, which satisfies the design requirement to achieve a static MTF higher than 0.2. Moreover, the whole system structure is compact and its elements are easy to manufacture and align.