Fine mullite precursor was prepared by colloidal sol-gel processes. Aluminum isopropoxide [Al(i-OC3H7)3] as a starting material of Al2O3 and silicic acid extracted by THF from sodium silicate as a starting material of SiO2 were used. Sodium silicate was first acidified by dilute sulfuric acid to form silicic acid. ; followed by extraction using THF, Mullite precursor was synthesized by sol-gel processes from aluminum isopropoxide and sillicic acid considering the degree of extraction of Si and the removal efficiency of Na. The impuri쇼 content of silicic acid extracted by THF was below 0.04% Synthetic mullite precursor consisted of 3Al2O3.2SiO2 and showd spherical particles of 0.05$mu extrm{m}$ diameter and below 0.462% of impurites. The mullite precursor was characterized by EDS, XRD, TG/DSC SEM, FT-IR spectroscopy ICP and TEM