Polypropylene (PP) flammability poses an impact on the environment and safety, making the development of environmentally friendly and efficient halogen-free flame retardants essential. Type Ⅱ Ammonium polyphosphate (APP) has poor thermal stability, hence it needs for modification research. In this study, new phosphorus-based flame retardants were prepared by mixing and coating at different temperatures for the evaluation of their effects on the mechanical and flame-retardancy of PP materials. The results showed that the flame retardant prepared from type Ⅱ ammonium polyphosphate, melamine and silane coupling agent KH560 according to the mass ratio of 3∶1∶0.01 mixed at 200 ℃ for 60 min in a high mixer had the best and stable mechanical and flame retardancy. The maximum heat release rate (MARHE) of these materials was reduced to 249.96 kW/m², the heat release rate (HRR) was reduced to 85.75 kW/m², the mass loss rate (MLR) was reduced to 1.78 g/(s·m²), the total heat release heat (THR) was reduced to 68.04 MJ/m², the total smoke production (TSP) was reduced to 9.07 m², and the time to ignition (TTI) was extended to 33 s. The flame retardant is highly efficient and environmentally friendly, and the modified PP material meets the requirements of flame retardant industry standards.