Abstract: Small angle X-ray scattering(SAXS) with synchrotron radiation as X-ray source is used to study the pore structure of Fe_2O_3 xerogels prepared by sol-gel procedure and then heat-treated at different temperatures.By analysing the distribution of diameters of the pores, specific surfaces and fractal behaviors in samples, the characters and mechanisms of pores growing are discussed. The results show that the pores in Fe_2O_3 xerogels are polydisperse and the structure of the pores is mass fractal. With increase in heat-treatment temperature,the average size of diameters of the pores and the dimension of fractal of Fe_2O_3 xerogels are increased, whereas the scale range possessing fractal behavior become narrow.