The surface states of sol-gel derived PbTiO3 thin films on Si substrates before and after Ar1 sputtering were studied by x-ray photoelectron spectroscopy (XPS). The results showed that there was no residual carbon or other impurity element in the films except some carbon surface contamination due to specimen handling or pumping oil. A large amount of absorbed oxygen was near the surfaces of the films. The chemical composition of the films was found to be stoichiometric, as proved by inductively coupled plasma results. The valence states of the ions indicated that the films were PbTiO3 with perovskite structure. The XPS spectra of the films after Ar1 sputtering for 10min differed greatly from those of as-prepared films. This probably results from the preferred sputtering of lead atoms and the production of many new dangling bonds during Ar1 bombardment.