The effect of copper concentration on the performance of the catalytic reaction between silicon and methyl chloride was investigated using online gas chromatogram. The catalyst concentration greatly influences various aspects of the direct organosilane synthesis process, including the reaction rate, the selectivity, and the silicon conversion. The reaction activity and the silicon conversion increase as the catalyst concentration increases. However, the reaction selectivity decreases for the catalyst concentrations more than 9 wt.%. The cross-sections of deactivated contact mass particles were observed by optical microscopy and analyzed by scanning electron microscope combined with energy dispersive X-ray detector (SEM-EDX). The observations showed that a textured substance formed on the original flat surface of the silicon particles after deactivation with copper only in a shallow surface layer of the contact mass. This indicates that the copper diffusion is the rate limiting step which causes the reaction deactivation.