At monolayer coverage of Pd on Ru(0001) surface, the core-level spectra of Pd 3d shows a positive core-level shift of X-ray photoelectron spectroscopy (XPS) while the d-band center of valence band spectra moves away from Fermi level in comparison of bulk Pd(111). The modification of electronic structures, displayed in core-level and valence band XPS spectra can be explained with substrate-induced charge polarization effect in Pd layer, resulting in lowering average potential around atom. (C) 2011 Elsevier B.V. All rights reserved.