Abstract: In this paper SSIMS (Static Secondary Ion Mass Spectrometry) combined with XPS was used for measuring the surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3. Because of very high surface sensitivity, SSIMS has been used successfully in characterization of the surface state or species of active component supported on the surface of the carrier (TiO_2-Al_2O_3), as measuring the intensity ratios (e.g. I_(114_(MoO~+))/I_(27_(Al~+)), I_(59_(Co~+))/I_(27_(Al~+)), etc.) of different secondary ions. Also, SSIMS has been used for determining the constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3, as measuring the intensity of secondary ion as a funcnion of time (e.g. I~(114)MoO~+(t), I~(59)Co~+(t), etc.). The results of the dispersed amount of active component MoO_3 on the surface of carrier by SSIMS are in line with those obtained by PASCA (Positron Annihilation Spectroscopy for Chemical Analysis) and LRS (Laser Raman Spectroscopy). Furthermore, the results of surface state and constitution of selvage layers of novel supported catalysts MoO_3-CoO/TiO_2-Al_2O_3 can be correlated with the HDS (hydrodesulfurization) reactivity of thiophene at the atmosphere pressure. And the satisfactory result was obtained. All these mentiond above illustrate that after improving some experimental techniques, the SSIMS can be used as a powerful tool for measuring the surface state and the constitution of selvage layers of supported catalysts simply and directly.