Method for extracting silica from herbaceous plants

A method for extracting silica from herbaceous plant capable of extracting high purity amorphous silica from seed shell of various herbaceous plants is provided. The method includes carbonizing a herbaceous plant and pulverizing a carbide of the plant to a size of at least 50 mesh, adding at least 5% (w/w) aqueous alkaline solution based on 100 weight percents of the carbide, leaving a reactant of the solution and the carbide for 1 hour at about 45° C. and filtering the reactant, slowly heating the reactant to a predetermined temperature, dropping sulfuric acid to the reactant at the predetermined temperature until the sulfuric acid is neutralized, and evaporating and drying the reactant to produce silica.