As one of the most important development of remote sensing, spectral imager has been widely used in military, geognosy, ocean and atmosphere measurement. However, the classic spectral imager, neither dispersive spectral imager nor Fourier transform spectrometer, which has to take multiple exposures to scan spectral data cube, do not suit with the situation that the scene change too fast. Four-dimensional (4D) fiber reformatting spectral imager, in which a special optical fiber bundle sits in the image plane of the telescope and has linearly aligned at the entrance to the spectrograph, can capture three-dimensional (3D) spectral data cube in a single exposure. So it enable to measure fast moving target or fast changing scene. A breadboard system in the laboratory is described, the average spectral resolution of the system is 4.2 nm in visible range, and a good imaging result of color target is got. The fiber bundle errors are analyzed, and the calibrating method is given.