Kaolinite was synthesized through th acid treatment of mixture which consisted of psudoboehmite and colloidal silica in hydrothermal reaction at $213^{circ}C$ under autogeneous vapor pressure. Crystallization process was characterized by X-ray powder diffraction pattern, IR spectra and Hinckley index was calculated. The synthesis in acidic solution promotes the dissolution of the starting materials and leads to crystallization of kaolinite. The rate of crystallization to kaolinite and stacking defect were found to e affected by kind of anion, acidity and starting materials.