Abstract: The application of ionic liquids (ILs) in metal extraction and separation is one of hot-topic research. Compared to conventional organic extractants, the ILs have many excellent properties of nonflammability, low volatility, negligible vapor pressure and low water solubility, etc. The quaternary-ammonium-salt-type ILs have the advantages of simple synthesis, low cost and low toxicity.Theyare an important type of ILs for extraction and separation of metal ions.The types and mechanism of the quaternary-ammonium-salt-type ILs were summarized.The research on extraction and separation of metals with these ILs was reviewed, including rare earth, radioactive elements, rare dispersed elements, heavy metals and transition metals.Their future research was proposed.