Based on spontaneous combustion temperature programmed experiments of No. 2 coal sample in Yangdong Mine and Yangquhe Mine, concentration curves of six kinds of gas -CO, CO2, CH4, C2H4, C2H and C3H8 were given. The difference existed in oxidized spontaneous combustion characteristics of coal from different regions in same coal seam. CO was considered as main sign gas causing spontaneous combustion of Yangdong Mine, with CO2, CH4, C2H and C3H8 as supplementary sign gas, C2H4 and C2H2 as affirmed index sign gas. The index system of spontaneous combustion gas of Yangdong Mine was founded. Discriminant parameter of oxidation of coal seam spontaneous combustion gas was confirmed according to release volume of CO, providing reliable basis to formulation of technical safety measures of preventing coal spontaneous combustion layer.