Samples of metal-dielectric multilayer films are post-annealed at different temperatures. It is experimentally found that at the annealing temperature of 350 ℃, a transition layer between Au layer and SiO2 layer of the samples occurs, and these samples possess the strong anti-chemical-cleaning ability. Based on the investigation by a transmission electron microscope and the analysis by an energy dispersive spectrometer, it is found that the occurrence of transition layers is mainly the result of Cr atoms diffusing from the Au bottom layer to the SiO2 layer. The transition layer can enhance the adhesion between the Au layer and SiO2 layer and block the infiltration of acid solutions, thus the anti-chemical-cleaning ability of metal-dielectric multilayer films is enhanced.