The invention discloses a foreign substance detection system based on spectral imaging and a foreign substance detection method based on the spectral imaging. The detection system comprises a lighting system, a spectral imaging device and a computer, wherein the lighting device is used for irradiating from a position above a detection table and providing uniform illumination for an object to be detected; the spectral imaging device is used for rapidly acquiring a spectral image of the object to be detected in any spectral channel in the wave band range of 400-1100nm, has the imaging frame frequency range of 1-1000 frame/second and the spatial resolution of 10-1000 microns, and is used for transmitting an obtained spectrum into the computer; the computer is used for receiving the spectral image output by the spectral imaging device and comparing a spectral image of a sample with the measured spectral image so as to judge whether a foreign substance exits at the difference point of the spectrum or not. After the system and the method are adopted, image information of a target can be obtained, and spectral information of the target can be also obtained; the foreign substance can be distinguished out from the background according to the difference between the background and the spectral information of the foreign substance; for the condition that the background and the foreign substance have the similar shapes and colors, the system and the method have the advantages of being real-time, rapid, high in recognition rate, and capable of being widely applied to a detection line of nickel foams.