A hydrophobic precipitated silica is prepared by a process comprising: a) preparing a mixture of an organopolysiloxane derivative and a precipitated silica; b) conditioning the mixture obtained at a temperature ranging from 10 to 150.degree. C. for a period ranging from 0.5 to 72 h, and c) conducting oxidative heat treatment under fluid conditions at a temperature more than 300.degree. C. with an oxidizing gas.