Abstract: The invention relates to a process for the simultaneous extraction of lignin and silica from lignocellulosic plant material, characterized in that it comprises the steps of: a) fractionating the lignocellulosic plant material in the presence of an acid solution, so as to obtain a solid fraction comprising cellulose, residual lignin and silica; b) extracting simultaneously lignin and silica from the solid fraction obtained in step a) with a basic solution, at a pH between 10 and 13 and at a temperature between 70° C. and 90° C., so as to obtain a liquid phase comprising lignin and silica, and a solid phase; c) separating the liquid phase and of the solid phase obtained in step b), d) coprecipitating a mixture of lignin and silica comprised in the liquid phase, at a pH between 5 and 6.