In the present works the porous structure of silica particle was modified to the more open-packed net-work of particles to provide greater porosity and pore radius by transfering nitric acid from the continuous phase of TBP(tributyl phosphate)-ethanol containing nitric acid into the drops of sodium silicate aqueous solution, where the soluble silica was transformed into active silica, simultaneously polymerized to the porous network of silica particles. The structural characteristics of silica were improved to have large pore radius of 0.2-40㎛, high pore volume of 3.0-4.1cm³/g and specific surface area of 20-800m²/g by inceasing the diameter of primary particle and the rate of production of active silica. The resulting structural characteristics were compared to the particle formation model bas-ed on the mass transfer rate of nitric acid and the polymerization kinetics of soluble silica, and the systematic research results presented valuable information about the mechanism of particle formation and the porous structure of silica.