Abstract: Common direct pyrolysis process for foamed polystyrene(PS)produces no carbonized materials. Two-stage experiments—sulfonation followed by cabonization, were carried out to realize carbonization of foamed polystyrene. Thermoanalysis and elemental analysis were used to characterize the processes and products. The results showed that relative contents of sulfur and carbon in the aimed products increased with increase of carbonization temperature, while relative contents ofhydrogen and oxygen were on the contrary. At carbonization temperature of 600℃, the relative contents of carbon, sulfur andhydrogen were 75.34%, 9.95% and 1.52%, respectively. The yield of carbonized material was about 80%, ash content was lower than 0.1%, volatiles ranged 10.9%-12.1% and fixed carbon 87.9%-89.1%. Such carbonized material could be used as precursor for preparation of activated carbons with various potential uses.