L ost foam casting, a near net shape and green casting technology, have various advantages, like high precision, high surface quality, environmental cleanliness, simple process and so on [1-4]. However, in ordinary sand casting, the foam would experience complex physical and chemical reactions with gasification and decalescence in the high temperature eff ect of molten metal during the fi lling process. These reactions will decrease temperature rapidly in the metal front and produce backpressure causing a huge impact on fi lling and even causing casting defects [5-8]. In order to further understand the fi lling mechanism of lost foam casting, a great number of studies have been made to explore the pyrolysis characteristics and thermal kinetics of diff erent kinds of foam patterns. Shivkumar S. et al. [9, 10] have investigated foam degradation of EPS and EPMMA since the 1980s. They used scanning electron