Abstract: There has been a dramatic growth in ionic liquids research over the past decade and a large number of novel ionic liquids with a wide range of application have been discovered. Since ionic liquids are recognized as green solvents，the research is focused on their synthesis，physicochemical properties and application，and not on their degradation，toxicity and corrosivity，which are directly related to environmental protection. This review addresses these key issues and highlights the research directions and outlook of ionic liquids.