A facile and novel approach is provided to improve the dispersion of large-size reduced graphene oxide (LRGO) in a polymer matrix through attachment on the surface of ammonium polyphosphate (APP) in the medium of (3-aminopropyl) triethoxysilane (APTS). Here, a series of LRGO-wrapped APP (named LRAPP) were first prepared and successfully characterized and then blended into thermoplastic polyurethane (TPU). The introduction of LRGO increased the interfacial adhesion between the APP and polymer, thus achieving remarkable enhancement in mechanical and flame retardant properties. Especially TPU/LRAPP1, where APP is encapsulated by 1% LRGO, can obtain a huge increase in tensile strength and elongation at break (189.7% and 24.6%, respectively) compared to those of TPU/APP. In addition, LRAPP0.5 encapsulated by only 0.5% of LRGO could effectively restrain the melt dripping phenomenon in TPU composites and acquired the lowest peak heat release rate value of 170.6 kW/m(2). This novel strategy aims to broaden extensive application of large-size graphene.