Oxidation reaction of hydrosilane catalyzed by Wilkinson’s catalyst can produce hetero-disiloxane compounds. Herein, we investigated the kinetic constants of the reaction of triethoxysilane with oxygen in the presence of Wilkinson’s catalyst at 100 °C in toluene. The kinetic rate constants of elemental reactions, which are expected in this reaction system, were evaluated to reproduce the time-dependent variation of peak areas in gas chromatography. The rate constant of silanol-formation via oxidation reaction of TES was estimated to be 0.045 L^1/2 mol^−1/2 min⁻¹. The rate constant was smaller than that of general aqueous hydrolysis reaction of alkoxysilane. The rate constants of alkoxy-silanol and silanol-silanol condensations were 0.12 and 0.08 L mol⁻¹ min⁻¹, respectively. The silanol-formation reaction was estimated to be the rate-determining reaction to form pentaethoxydisiloxane as a major product. The side-reactions to form 1,1,3,3-tetraethoxydisiloxane and hexaethoxydisiloxane were found to be suppressed by the formation of water in small amount.