Sawdust is a common by-product of wood processing industry. Spontaneous combustion would even take place under unfavorable conditions of storage and transportation. In this study, self-heating substances test experiments, Thermogravimetry (TG) experiments and Frank-Kamenetskii (FK) theory were used to compare the spontaneous combustion risk of three sawdust samples (DCP, CFE, and LOH). The results revealed that the Critical Ambient Temperatures (CATs) of DCP, CFE and LOH were 81.2 ( +/- 0.3), 96.0 ( +/- 0.4) and 125.9 ( +/- 0.3)degrees C respectively when the stack dimension reached 1.6 m. Lower CAT for sample indicated that it had a higher spontaneous combustion risk. On the other hand, the relationship between spontaneous combustion risk and soluble components of three sawdust samples was studied with Gas Chromatographic and Mass Spectrometric (GC MS) experiments. The results found that if a sawdust sample contained more soluble components than other sawdust samples, the spontaneous combustion risk of this sample would also higher than other sawdust samples, and vice versa.