Abstract: Vapor phase carbonylation of methanol was investigated over NiPd/AC catalyst under the conditions of 260℃, 1.5MPa, CO/CH3OH/CH3I(mol ratio)20/19/1, W/F=7.5g·h·mol-1. The structure and surface property of the fresh and deactivated NiPd/AC catalysts were characterized by BET specific surface area, PyrolysisFTIR and XPS. It was found that the deactivation at the primary step appeared to be consistent with a strong adsorption of reaction products that plugged the catalyst pores and leaded to diffusion limitation. With the proceeding of the reaction, the carbonylation active site Ni migrated gradually and enriched on the catalyst surface, resulting in easy carbon deposition, which enhanced the deactivation of the catalyst. Further investigation revealed that the carbon deposited on the catalyst surface has graphite structure or similar to graphite structure.