Abstract: A composite of polypropylene (PP) with pentaerytheritol phosphate ester melamine resin salt (PPEMR) with acrylic resin as a compatibilizer was prepared and its fire-retardant behavior was investigated. Rheological testing and scanning electron microscopy observation indicated that when the content of AR was between 2.5 phr and 3.75 phr, the melt viscosity of the composite was the highest. During burning, a foam char layer was formed.Thermal analysis and infrared spectra showed that carboxylic acid group of AR reacted with the -NH2 of PPEMR, which retarded the degradation and leaded to a comparatively thermal stabilization of the composite. The higher the melt viscosity, the easier the formation of the foam char layer. Thermal analysis curve assumed that the heat release process was delayed, and the heat release temperature range was broadened.