The traditional effective development technology of heavy oil resources is facing increasingly severe challenges of safety，environmental protection and economy. As a green solvent for heavy oil recovery at room temperature，ionic liquid has great potential. The concept and physicochemical properties of ionic liquids are described. The development of ionic liquids is reviewed. This paper summarizes the research progress and understanding of ionic liquid as viscosity reducer，dispersant，in-situ modification and displacement experiment. In view of the existing problems in the current research and the actual situation of the oil field，the application target of ionic liquid is the resources that can't be economically and effectively exploited by the existing thermal recovery technology and the heavy oil reservoir that needs to be enhanced recovery after steam injection development. As a new generation of in-situ modification and viscosity reduction technology for heavy oil，ionic liquid has great application potential. It should be used as an advanced reserve technology to speed up research and development.