Abstract: In SIMS profiling of GaAs in which Si well-distributed and Si-implanted,the RSF of Si in GaAs coinciding with the value in manual bas been obtained via the methods such as the reference sample in homogene-ous volume,the integral of secondary ion intensity in profile,as well as the calculation by LSS theory.The RSF is also applied to quantitatire analysis of Si-implanted GaAs witli double-energies and double-doses,and Si-doped MBE multilayers GaAs.The influence of oxygen,carbon in GaAs on secondary ion signals of 28Si^-,103SiAs and the Linear relationship of 28Si^- to 103SiAs have been discussed.