Space remote sensing urgently requires wide-angle and high-resolution spaceborne imaging spectrometer. According to the research objective of wide angle and high resolution, the design method of firstly dividing field of view (FOV) and secondly dividing beam using dichroscope is developed. The principle of dividing FOV is analyzed. A reflective spaceborne imaging spectrometer is designed, which is composed of a pointing mirror, a 11.42° telecentric off-axis three-mirror anastigmatic (TMA) telescope and four Offner convex grating spectral imaging systems. The proper magnification is chosen for each spectral imaging system to match two types of detectors. Ray tracing and optimization are performed and analyzed by CODE V software. The results demonstrate that the modulation transfer function (MTF) for different spectral bands is more than 0.7, which satisfies the pre-designed requirement. The design method is proved to be feasible.