Auger electron spectroscopy (AES), X-ray photoelectron spectroscop (XPS) and ultraviolet photoelectron spectroscopy (UPS) have been used to study the InSb(lll) surfaces treated with (NH4)O2Sx. It is found that after the sulfide treatment, the sample surfaces are covered by a thin overlayer of sulfide (8?), which prevents the sample surface from oxidization and carbon contamination in the air. XPS and UPS results show that S atoms bond to both Sb atoms and In atoms on the sample surfaces. Sb-S bonding peaks in the Sb3d spectra exhibit a core level shift of 1.9eV, the bonding of S to In atoms causes an In4d core level shift of 0.6-0.7eV. A thermal annealing at 350℃ gives rise to the decomposition of Sb-S bonding and the evaporation Sb atoms from the sample surfaces. In-S bonding can not be decomposed completely by annealing up to 500℃ and a small amount of S atoms remains on the sample surfaces in the form of indium sulfide.