Abstract: The deactivation of PdCl₂-CuCl₂-KOAc/AC catalyst for gas-phase direct synthesis of dimethyl carbonate and the effects of reaction conditions on the catalyst stability were studied.The possible active centers were Pd²⁺ and Cu⁺.Treating the catalyst with chloro-organic compounds could increase the content of Cu²⁺ and Pd²⁺ on the surface of the catalyst.Cu2+ is the oxidant of Pd⁰.The synergistic effect between Pd and Cu could complete the oxidation-reduction cycle between Pd²⁺/Pd⁰ and Cu²⁺/Cu⁺.With the loss of Cl^- anion ,the ratios of both Cu²⁺/Cu+ and Pd²⁺/Pd⁰ were changed.This change was one of the main reasons for the reversible deactivation of the catalyst.The loss of Pd component, carbon deposition and aggregation of metal particles were the main reasons for the irreversible deactivation.The stability of the catalyst could be improved by increasing the reaction temperature or by lowering the reaction pressure and the concentration of oxygen in the feed.The chloro-organic compounds added in the feed could increase the service time of the catalyst effectively.The activity could be kept stable for more than 150 h at the STY of 700～750 g•L^-1•h^-1 when the reaction pressure was 0.3 MPa and the concentration of the chloro-organic compound was 5%(vol).