A method for extracting spectral information of a substance under test includes: identifying a pixel region A(x, y) occupied by an object under test from a hyperspectral image acquired; extracting a specular reflection region Aq and a diffuse reflection region Ar from the pixel region A(x, y), and calculating a representative spectrum Iq(ω) of the specular reflection region Aq and a representative spectrum Ir(ω) of the diffuse reflection region Ar, respectively; by comparing each element in the representative spectrum Iq(ω) of the specular reflection region Aq with each element in the representative spectrum Ir(ω) of the diffuse reflection region Ar, separating information of a light source from spectral information of the object to obtain a first spectral invariant C(ω). This method does not require additional spectral information of the light source, which improves the analysis efficiency.