The invention discloses slicon dioxide 
aerogel, as well as a continuous constant-pressure 
drying preparation method and a 
system thereof. The preparation method comprises the following steps of: using water glass, silicasol, 
silanol and the like which are relative low in price as 
silicon sources, uniformly mixing the 
silicon sources, water, a catalyst and a 
drying control agent to obtain a mixture, leaving gel to stand, crushing the wet gel into particles or 
powder, performing replacement with 
alcohol and liquid 
alkane, using a hydroghobing agent for modification, separating 
alkane gel, and finally, performing 
drying and 
sintering so as to obtain 
dewatering silicon dioxide 
aerogel. The 
silicon dioxide aerogel disclosed by the invention can realize 
continuous production, and is short in preparation period, small in 
pollution, low in cost and environment-friendly. The aerogel is 
powder or particles, the density is 0.04g / ml-0.3g / ml, the particle 
diameter is 0.1 mum-2mm, the specific surface is 500m<2> / g-1200m<2> / g, and the heat 
conductivity is 0.01W / mk-0.04W / mk.