Abstract: A novel intumescent flame retardant (IFR) was prepared by combining ammonium polyphosphate (APP) with a self-made novel organic-metal hybrid char-forming agent (SCTCFA-ZnO), and then the intumescent flame retardant polypropylene (PP) composites were prepared by using this IFR through melting blending. The synergistic effects of APP and SCTCFA-ZnO on the flame retardancy and thermal degradation of PP composites were investigated by the means of limited oxygen index, vertical burning test, cone calorimeter test, thermogravimetric analysis and scanning electron microscopy. The results indicated that the PP composites achieved a UL 94 V-0 classification in the vertical burning experiment and an limited oxygen index of 31.1 % when 25 % of IFR was incorporated at an APP/SCTCFA-ZnO mass ratio of 2/1. Cone calorimetric results also indicated a reduction in flammability parameters due to a combination of APP and SCTCFA-ZnO for PP composites. Thermal analysis indicated that the presence of IFR improved the thermal stability and char-forming ability of the composite. Morphological observation demonstrated a compact and continuous intumescent char layer formed on the composites, which improved the flameretardant properties accordingly.