Abstract: The NaY zeolite with different sizes was synthesized using sodium aluminate and silica sol as the main raw materials without seed gel. The NH₄Y zeolite was prepared with ion-exchange of NH₄NO₃ from the as-prepared NaY zeolite and used as support to prepare the CuY catalyst through vapor impregnation. The CuY catalyst was characterized with XRD, TEM, BET and XPS and used to catalyze the oxidation carbonylation of methanol to dimethy carbonate. The effect of the support size on the catalytic activity was investigated. The results showed that the grain size of support affected the pore structure, especially the formation of mesopore, and the catalytic activity in turn. When the grain size was 500 nm, the intergranular pore is conducive to forming dimethy carbonate and the CuY catalyst exhibited an excellent catalytic activity with the space time yield based on methanol being 273.1 mg/(g·h), percentage of methanol conversion being 6.5% and selectivity of DMC being 72.1%.