The irradiation effects of Ar + , He + and S + with energy from 10 eV to 180 eV on n-InP(100) surface are analyzed by X-ray photoelectron spectroscopy and low energy electron diffraction. After irradiation on the n-InP surface, damage on the surface, displacement of the Fermi level and formation of sulfur species on S + exposed surface are found and studied. Successive annealing is done to suppress the surface states introduced by S + exposure. However, it is unsuccessful in removing the damage caused by noble ions. Besides, S + ions can efficiently repair the Ar + damaged surface, and finally form a fine 2×2 InP surface.