Small angle x-ray scattering technique was used to analyze the variation of microstructure parameters of precipitates in an Al-Zn-Mg-Cu-Li alloy aged at 130, 150 and 160℃ for the same duration. Precipitate particles’ radius increased with aging temperatures, but their specific inner surface and integrated intensities decreased with aging temperatures. The study on Porod curves q3J(q)-q2 indicates that there is a sharp boundary between precipitates and the matrix.