Abstract: A polyurea-chlorocyclophosphazene microcapsule flame retardant was prepared by interfacial polymerization with 2,4-toluene diisocyanate (TDI) and hexanediamine as the raw materials. Thermogravimetric analysis (TGA) test showed that the thermal decomposition temperature of chlorocyclophosphazene microcapsule steeply rose up as compared with chlorocyclophosphazene. Chlorocyclophosphazene microcapsule had better flame retardancy and smoke suppression than chlorocyclophosphazene when used with polypropylene(PP). Mechanical properties of chlorocyclophosphazene microencapsule/PP composites were superior to those of chlorocyclophosphazene/PP.