Abstract: The paper gives a theoretical method of applying Brillouin scattering principle to detect spatial object.The properties of Brillouin scattering of atmosphere,metal coat of spatial object and concealed material are calculated,analyzed and compared.The result shows that the discrepancy of the frequency shifting of atmosphere,metal coat of spatial object and concealed material is at least more than 10 times,thus it is applicable to use Brillouin scattering to detect spatial objects.The article not only calculates the frequency shifting,but also studies the technique for detection,and adopts a technique of using narrow-band quantum optical filter system to distinguish the scattered light accurately.