The invention discloses an inorganic sensitive layer based surface enhanced Raman spectrum detection technology and material preparation thereof. According to the detection technology, a surface enhanced Raman spectrum material based on an inorganic sensitive layer is used as an active substrate of a surface enhanced Raman scattering, and is exposed in the small molecule atmosphere; a new solid substance formed by specific reaction of the inorganic sensitive layer and small molecules to be detected by a Raman spectrometer is detected, and the type of the small molecules is obtained according to the Raman spectrum of the new solid substance; according to the preparation method, a colloid electrostatic self-assembly method, a thiourea-induced isotropic shell growth method, a metal halogenation method and a physical deposition method are used for a precious metal nanoparticle colloidal solution, a metal salt solution and a thiourea solution to prepare the material in which precious metalnanoparticles are coated with a metal oxide layer, or the precious metal nanoparticles are coated with a metal sulfide layer, or the precious metal nanoparticles are coated with a metal halide layer.The technology can be used for real-time online detection of hydrogen sulfide, carbon disulfide, hydrogen chloride, mustard gas, nitrogen dioxide and the like.