Abstract: Ball-milling the mixture of black phosphorous (BP) and zinc hydroxyl stannate (ZHS) was carried out to prepare ZHS-BP nanocomposite, which was then introduced into polypropylene (PP) matrix as flame retardant via melt blending. The thermal stability, combustion and mechanical properties of the PP based composites were investigated. Results show that the addition of BP and ZHS could increase the carbon residue of PP, and only 2wt% BP increases the limiting oxygen index (LOI) of the BP/PP composite from 19.7% (for pure PP) to 23.8%. Moreover, BP can effectively reduce the peak heat release rate (PHRR) and total heat release (THR) of BP/PP composite, the values of which are decreased by 32.52% and 17.80% respectively compared with that of pure PP. However, the release of toxic gases from PP combustion is increased obviously as BP is added, ZHS was then introduced as the assistant agent to suppress the smoke release. As a result, the average specific extinction area (av-SEA) and CO emission of ZHS-BP/PP are decreased by 15.42% and 29.76% respectively compared with BP/PP. Mechanical properties test shows that merely adding BP or ZHS has negative effect on the mechanical properties of the composites. However, the addition of ZHS-BP nanocomposite effectively improves the mechanical properties. Compared with BP/PP, the tensile strength and breaking tensile ratio of ZHS-BP/PP composites are increased by 12.51% and 4.04%, respectively.