The Heck coupling of iodobenzene with olefins occurs with high efficiencies at low temperatures inimidazolium-based ionic liquids catalyzed by PdCl2/Et3N, and the catalyst can be recycled after extraction ofthe products by supercritical CO2. The coupling efficiency is dependent on water content of the ionic liquid.With a low water content (<50 ppm) in the ionic liquid, the Heck coupling reaction would proceed with>90% yield at room temperature using this catalytic system.