The growth of Gd film on Ni(110) surfaco was studied by synchrotron radiation photoemission spectroscopy and XPS techniques. It is revealed that in the coverage range of 0—0.22 nm Gd4f core level showed a single-peak structure, therefore Gd film grows over Ni(110) in the layer-by-layer mode. However, when Gd coverage was larger than 0.22, nm the Gd4f peak turned gradually into double-peak and a double-peak structure with 2.3 eV separation was formed at 1.51 nm, meanwhile similar phenomenon was observed in the Gd4d XPS spectra. It is suggested that the double-peak structure of Gd4f was derived from the growth of Gd film in cluster mode and the Gd atomic clusters may exhibit different electronic states from Gd metal owing to their special structures. The Gd4f double-peak evolved into a single-peak on annealing at 600 K, implying that Gd clusters are thermodynamically unstable. The growth of Gd film on Ni (110) surfaco was studied by synchrotron radiation photoemission spectroscopy and XPS techniques. It is revealed that that the coverage range of 0-0.22 nm Gd4f core level showed a single-peak structure, therefore Gd film grows over However, when Gd coverage was larger than 0.22, nm the Gd4f peak turned gradually into double-peak and a double-peak structure with 2.3 eV separation was formed at 1.51 nm, meanwhile similar is was observed in the double-peak structure of Gd4f was derived from the growth of Gd film in cluster mode and the Gd atomic clusters may exhibit different different states from Gd metal due to their special structures . The Gd4f double-peak evolved into a single-peak on annealing at 600 K, implying that Gd clusters are thermodynamically unstable.