Abstract: A mesoporous SBA-15/silica composited aerogel was prepared by a two-step acid-alkali method with SBA-15 as an additive. The effects of the amount of SBA-15 on the formation process and the performance of the eomposited aerogel were investigated. The microstructure of the composited aerogel was characterized by scanning electron microscopy and N2 adsorption-desorption isotherms, and the mechanical properties and thermal conductivity were tested. It is found that as a small amount of SBA-15 is added, the gelation time of silica greatly shortens, the mechanical properties improves, the thernlal conductivity still keeps small, while the specific surface area slightly decreases.