A new method is proposed for determining the backscattering factor using information provided by the background off an direct Auger spectrum N(E). Complicated calculations such as the Monte Carlo method were avoided, and the quantitative Auger analysis accuracy could be further improved since the calculations of backscattering factor was based on the spectra. The examples of determining the compositions of Au-Cu and Ag-Cu alloys are given. These results are compared with that obtained by other mothods.