A novel flame retardant system, embraced shell (S) and histidine diphosphate (H) as intumescent flame retardant developed in the Department of Chemical, Biological and Aerosol Hazards laboratory, was added to the epoxy resin and examined. The influence of flame retardant system on the thermal stability was assessed based on thermogravimetric analysis (TGA). Moreover, the flame retardant components were characterized by grain size distribution. It was found that the incorporation of the developed flame retardant system caused the formation of thermal stable char, which may inhibit the burning process.