Nano porous material SiO2 aerogels can not only be used as a low temperature Nuclear Target in ICF but also be used as an adsorbent of HTO vapor. BET，SEM，Pore Size Distribution and TEM techniques were used to characterize the morphology and pore structure of the low-density silica aerogels. Gas adsorption of the lowdensity silica aerogels was measured for the samples with various densities（18.6～200 kg·m-3）. Measurements were done at various pressure drops with water and benzene. The results of the adsorption isotherms were analyzed with BET multilayer adsorption theory．