Al2O3-SiO2-based Co(Ni)-Mo(W)-S catalysts are widely investigated hydrodesulfurization (HDS) catalysts in recent decades. XPS is a suitable technique to detect the surface properties of HDS catalysts. Typical overlapping spectra in the XPS analysis of HDS catalysts, such as Mo3d and S2s, Si2p and bremsstrahlung-induced Al KL23L23 using nonmonochromatic AlK alpha source, W4f and W5p(3/2), as well as the disturbance of Auger lines on Ni2p and Co2p, are carefully studied in the present paper. Besides, effective methods to overcome the influence of peak overlaps are illustrated. These results would provide basic and important information in interpreting XPS results of HDS catalysts. (C) 2009 Elsevier B. V. All rights reserved.