In recent years, phosphonitrile are emerging as a new type of flame retardant, which is rich in nitrogen and phosphorus, and has high flame-retardant efficiency. The chlorine atom on Hachlorocyclotriphosphonitrile has high reactivity, and it can react with benzene ring and other groups to improve the compatibility with the base material. Chlorine atoms can also react with groups containing other flame-retardant elements (such as Si, S, etc.) to improve flame retardant efficiency through synergistic action. In addition, phosphoronitrile with the active group at the end can copolymerize with the base material to form a highly crosslinked structure, so as to reduce the degradation of the thermodynamic properties of the base material. Cyclophosphonitrile can also be used as a framework for the synthesis of micro-nanomaterials because of the multiple reactive sites on its single molecule. Recent studies have shown a new direction, introducing some groups with special properties at the active site of cyclotriphosphonitrile, which can provide phosphonitrile compounds with other properties in addition to flame retardant properties, such as water absorption resistance, insulation properties, etc. Based on the structure of phosphonitrile, this paper has discussed the effects of the structure of phosphonitrile on flame retardancy and flame retardancy mechanism, and has made a preliminary prediction on the development direction of phosphonitrile compounds in the future.