Auger line-shape analysis is employed in the study of the chemical states of the GaAs/Si interface. A fast Fourier transform algorithm is applied to quantitatively analyze the concentration of a particular element in an interrupted structure, such as an interface and a surface. The data are corrected for spectrometer distortions and electron-energy-loss processes. The correction schemes are presented. The changes of the Auger radial matrix elements for core-valence-valence, core-core-valence transitions (CVV, CCV) are analyzed in different depth profiles of the GaAs/Si interface. It has been found that Si bonds predominantly to As instead of Ga. Some p electrons are transferred from the valence band of Si to As, and a new interface state emerges at 2 eV above the top of the valence band of GaAs. But for Ga, there are no observable changes, suggesting that Ga has no bonding with Si in the GaAs/Si interface.