A space-borne far ultraviolet imaging spectrometer working at the sun-synchronous orbit is studied, which is used to satisfy the scientific requirements of the connection and coupling detection between the low atmospheric driver and ionosphere. The instrument is designed to detect the spectral intensities of various particles in the ionosphere, which produce the characteristic radiation different at day and night in the far ultraviolet band, by the two-side lateral limb observation method. Then the influence of the low atmospheric driver is further acquired quantitatively. According to the detection mechanism, the observation scheme for instrument system is designed, the instrument performance parameters and system design, integration of prototype system, performance test, ground radiation calibration, and others are investigated. This research provides a new way in the future far ultraviolet imaging spectral observation of the ionosphere.