Small angle X-ray scattering (SAXS) with synchrotron radiation as X-ray source has been used to study the structure of silica xerogels prepared by sol-gel process. Both the agreement of SAXS profiles with and the deviation from Porod’s law and Debye’s theory have been found, showing that there are differences between the structures of these xerogels. The specific surfaces of the samples whose SAXS profiles agreed with Porod’s law and Debye’s theory have been determined by analyzing SAXS data according to the methods of Porod and Debye, respectively, and the results of both methods used were found to be similar. We have proposed the corresponding Porod and Debye analysis methods to determine the specific surfaces of samples whose SAXS profiles do not agree with Porod’s law and Debye’s theory, i.e. the negative or positive deviation. The results of both methods used here were also found to be close to each other. The specific surfaces fell between approximately 80-150 m2/cm3 for the samples prepared under Small angle X-ray scattering (SAXS) with synchrotron radiation as X-ray source has been used to study the structure of silica gel prepared by sol-gel process. Both the agreement of SAXS profiles with and deviation from Porod’s law and Debye’s theory have been found, showing that there are differences between the structures of these xerogels. The specific surfaces of the samples whose SAXS profiles agreed with Porod’s law and Debye’s theory have been determined by analyzing SAXS data according to the methods of Porod and Debye, respectively, We have proposed the corresponding Porod and Debye analysis methods to determine the specific surfaces of samples whose SAXS profiles do not agree with Porod’s law and Debye’s theory, ie the negative or positive deviation. The results of both methods used here also also found to be close to each other. The specific surfaces fell between approximately 80-150 m2 / cm3 for the samp les prepared under