The thermal behaviors and the flame-retardancy of styrene-ethylene-butadiene-styrene-block copolymer containing various additives were studied. The combustion was measured by the Underwriter laboratory (UL) test and cone calorimeter test and thermogravimetric analysis and program-mass spectroscopy were applied to analyze the thermal behaviors. The blend with halogen additives showed the best result in the UL test. However, the blend with red-phosphorous was the best in the cone calorimeter test. As the styrene sequence in the copolymer tended to degradate at a lower temperature, the major scission products spouted out from the polymer surface originated from polystyrene. The shorter the ignition times of the blends with red-phosphorous were, the lower the peak heat release rates were. It was an interesting phenomenon because it suggested that the chemical structure of the residue changed to more stable polymers. (c) 2007 Wiley Periodicals, Inc.