This paper reported the effect of the weak damage in the Al0.25Ga0.75As/GaAs epitaxial layer induced by 0.8 MeV Si ions implantation with ion dose from 1×1014 to 5×1015 cm-2. The Raman spectra measured on these samples showed that there were two kinds of phonon modes existing in the epitaxial Al0.25Ga0.75As films. The strains induced in the implanted layer and the corresponding lattice parameters were also evaluated as a function of the implanted dose. In addition, the Rutherford backscattering spectrometry/channeling (RBS/C) was also measured on these samples. These two measurement techniques all confirmed that the implantation only induced weak damage in the material.