Microcapsulated chlorocyclophosphazenes were synthesized, and then microcapsulated chlorocyclophosphazene/polypropylene(PP) composites were prepared. The results showed that microcapsulated chlorocyclophosphazene had good high thermal stability through thermogravimetric analysis (TGA). The flammability and mechanical properties of microcapsulated chlorocyclophosphazene/polypropylene composites were investigated by limiting oxygen index experiment, UL 94V flame retardancy test, cone calorimetry, tensile experiment, and impact test, respectively. It was shown that the microcapsulated chlorocyclophosphazene/PP composites had better tensile strength, impact strength, flame retardant properties and smoke suppress properties compared with chlorocyclophosphazene/PP composites.