Abstract: Al₂ O₃ films were deposited on thermally oxidized Si (100)substrates by ion beam assistant deposition(IBAD),and then implanted with 120keV,5×10¹⁵ cm^-2 Er ions.And then the samples were annealed at 773K to 1273K in Aren vironment for 1h.Photoluminescence and optical transmission spectra of all samples were measured with optical spectrometer Nicolet 860.PL intensity increases with the annealed temperature,and P L intensity of the sample annealed at 973K is the lowest and appears 1140nm peak.Optical transm ission spectra indicate that almost in all detected spectra the sample annealed at 973K corresponds to highest intensity and lowest abso rption.It is concluded that the lowest photoluminescence is due to changes in the pump absorption cro ss section,which is related to the minimum optical absorption of the Al₂O₃ materials.