The SiO2 ultrafine powder with high porosity and large specific surface area was prepared from sodium silicate and sulfuric acid as raw materials by parallel feedin chemical precipitation method. The basic performance of SiO2  powder had been characterized by means of BET、TGDTA and laser granularity analysis. Effective factors, including ways of materials feedin, sufactants and heating procedure were also investigated. The results indicates that the specific surface area of the prepared SiO2 powder is 823 m2/g, and the cumulative pore volume is 1.438 cm3/g.