A method for preparing organic carbonates comprising subjecting an alcohol compound to oxidative carbonylation in the presence of carbon monoxide, oxygen and a liquid-phase catalytic system, to form a organic carbonates, wherein the liquid-phase catalytic system includes at least one catalyst, at least one additive and at least one ionic liquid composed of a cation, which has a nitrogen-containing heterocyclic structure, and an anion. Through using the additive and the ionic liquid, the activity and the performance of the catalyst are enhanced, and increased reaction rate and yield can be obtained.