Abstract: This article reviewed the research progresses in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-type flame retardants and their applications in polymeric materials like epoxy resins, polyesters and polypropylene and also pointed out their future development direction. At the present, the development of DOPO-based flame retardants used for polymer are mainly focused on the direction toward low addition, multi-elemental flame-retardant synergy and no side-effect on the flame-retarded polymers. This type of flame retardants exhibit exhibits a good application prospect.