Nano porous material SiO₂ were prepared by acid-alkali two steps approach with low cost industrial silica sol as silicon source and deionized water as solvent. The surfactant was used as the surface modifier to get rid of the broken of samples in the drying process. The densities, specific surface area and the average pore size of the obtained SiO₂ monoliths are in the range of 150~400 mg/cm₃ and the range of 0.04~0.07W/(m.K), respectively. This method greatly reduced the cost in the preparation of SiO₂ nano porous material, which will largely promote the industrial production and application of porous SiO₂ materials.