The heterogeneous ethanol carbonylation of Ni supported on activated carbon (Ni/AC) is typically associated with significant activity loss, largely due to the facile occurrence of carbon deposition and Ni loss. In this study, the chlorine-containing Ni/AC catalysts were synthesized via the incipient wetness method and exhibited superior stability compared to catalysts without chlorine. Correlation of the catalytic performance and catalyst structure revealed that chlorine addition to Ni/AC reduced the amount of carbon deposition. Moreover, it is evident that there is a robust interaction between chlorine and Ni, as evidenced by XPS and H2-TPR, which can significantly impede the Ni loss during the reaction. The results of in-situ DRIFTS and CO-TPD experiments demonstrate that the addition of chlorine impedes the adsorption of iodine species on Ni/AC catalysts, which consequently affects the adsorption capacity of CO closely associated with the product selectivity.