Abstract: The effects of different crystal structures of copper chloride hydroxide on the catalytic synthesis of diethyl carbonate by the oxidative carbonylation of ethanol was discussed. The catalytic activity was improved significantly and the active component of γ-Cu₂(OH)₃Cl was partially converted into Cu(OH)Cl when KCl was added in the catalyst. CO-TPD analysis of the catalyst showed that the adsorption of CO increased and the desorption temperature shifted to the right. Morphological analysis by SEM of the catalyst showed that the active component of the catalyst was highly dispersed on the carrier promoting the catalytic activity of the catalyst in the synthesis of DEC. Reaction mechanism analysis showed that the fact that Cu(OH)Cl was more active than γ-Cu₂(OH)₃Cl in the oxidative carbonylation of ethanol to DEC was attributed to the John-Teller effect.