Because of the hydrophilic central cavities and hydrophobic external frameworks, 18-Crown-6 can form stable complexes with alkali metal ions, alkaline earth metal ions, lanthanides ions and organic ammonium. Therefore, 18-Crown-6 and other crown ether compounds have broad application prospects in such aspects as phase transfer catalytic reaction, ion sensor, selective separation of metal ions, antitumor research and the treatment of nuclear waste.