The disaster of coal spontaneous combustion mainly occurs in a concealed oxygen-poor environment in the underground coal mine. The formation law of hydrocarbon index gases can accurately reflect the degree of coal spontaneous combustion. In this paper, the influence of oxygen-poor degree on the formation law of hydrocarbon index gases was investigated by the program heating experiment of coal spontaneous combustion in different oxygen-poor environments. The results reveal that the rising tendency of the alkane index gas volume fraction can be reduced by the increase in oxygen-poor degree. Olefin index gases can predict the disaster of coal spontaneous combustion more reliably than alkane index gases in the oxygen-poor environment. As the optimal predictive index of coal spontaneous combustion in the oxygen-poor environment, the volume fraction ratios of olefins to alkanes can be used which increase steadily with the oxygen-poor degree.