Main reasons why flame retardant materials and flame retardants are widely used and rapidly developed are reviewed.The flame retarding characteristics and applicable area are analyzed for the flame retardant materials,such as halogen systems,organic phosphorus systems,phosphorus-nitrogen systems (intumescent flame retardants) and organic silicate systems.Particular attention is focused on retarding mechanism and retarding characteristics of the intumescent flame retardants and their development.To overcome drawbacks of the halogen flame retardant systems and improve their environment effects,some new non-halogen,low smoke,low toxic,and high efficient flame retardants and flame retarding technique are being developed,and it is considered that the research and development of intumescent flame retardants and organic silicate retardant systems will be one of the hottest research field in the 21 st century.