Preparation of aerogels via ambient pressure drying has well been acknowledged as an extremely important way to the development and application of high performance silica aerogels. Low density (<100 kg·m-3) and hydrophobic silica aerogels were successfully prepared via sol-gel process and ambient pressure drying by using tetraethyl ortho silicate as silica precursor. Various silica alcogels with different compression modulus were prepared by varying preparing parameters. Effects of preparing parameters on the compression modulus of silica alcogels and the density of as-prepared silica aerogels were studied. The preparing method of low density and hydrophobic aerogels by controlling the compression modulus of alcogels was accordingly explored. The results indicated that the low-density and hydrophobic silica aerogel (<100 kg·m-3) could be prepared by controlling the compression modulus of the Alcogels within the range of 0.25~2.5 kPa. This finding provided valuable guidance for the preparation and control of low-density and hydrophobic silica aerogels via low-cost ambient pressure drying.