In order to develop a gasifier of municipal solid waste (MSW), the basic characteristics of pyrolysis and thermal degradation of its gases derived from each component of MSW were examined. Tea leaf, cotton, paper, wood and fish meat decomposed rapidly in the temperature range of 550-650 K. For PE, PP and PS, the maximum rate of weight loss occurred in the temperature range of 600-750 K. For PVC, on the other hand, there existed two distinct steps of weight loss, which represented a lower (550-620 K) and a higher temperature (700-770 K) of decomposition. The gases derived in pyrolysis process at 770 K were further degraded during thermal degradation at 1020-1220 K for 5-15 s. Comparing between the amount of resultant tar before degradation at 1220 K for 15 s and after, average content of tar with molar fraction of 0.36 reduces to 0.03.