Effect of CuCl source and content on formation of triethoxysilane in the direct process is described and discussed. The two sources of CuCl and the contact masses from the reduction reaction by silicon and CuCl have been investigated by X-ray diffraction, scanning electron microscope and N2 adsorption-desorption with a purpose of studying the reasons that different CuCl sources cause different reaction effect. We found Si-Cu intermetallics in proportion to the contact area between CuCl and Si. So CuCl with the characteristics of finer particles and high specific surface area is beneficial to form vast scale active Si-Cu intermetallics. The CuCl concentration on the performance of the catalytic reaction between silicon and ethanol was investigated by online gas chromatogram. The catalyst concentration greatly influences various aspects of the direct synthesis of triethoxysilane, including the induction time, the reaction rate, the selectivity and the silicon conversion. The reaction activity and yield of triethoxysilane increase as the catalyst concentration increases. However, the reaction selectivity decreases when the catalyst concentration is more than 5%, in this case the yield of triethoxysilane is slightly lower than 10% catalyst concentration.