In order to study the influence of ash on the ability of coal spontaneous combustion, we used coal samples with different ash content to carry out temperature rising oxidation experiments in adiabatic oxidation device, and characterized the effects of the different ash content on the coal spontaneous oxidation process with 3 indicators (R₇₀, T_CPT, B). The results indicate that (1) the larger the ash content is, the slower the coal spontaneous oxidation process is. In low-temperature oxidation stage, the smaller the heating rate is, the higher the acceleration point of temperature-rising is and the more difficult the coal is to burn spontaneously. When the ash content is greater than 40%, the coal spontaneous combustion tendency is rapidly weakened. The acceleration point of temperature-rising is the accumulated results of temperature of zero-activation which reflects microscopic information, and it is intuitive and delayed. The larger the ash content is, the more obvious the lag is and the greater the difference in temperature is .(2) The relationship between ash content and the 3 indicators (R₇₀,T_CPT,B) is quadratic function. R₇₀ and T_CPT indicators show the larger the ash is, the weaker the coal spontaneous combustion tendency is, and that is in accordance with experience. Affected by the weight of water, B indicator shows when coal ash is less than 40%, the larger the ash content is, the stronger the coal spontaneous combustion tendency is, which is contrary to experience. Therefore, B indicator has certain limitations in the determination of the impact of ash on the coal spontaneous combustion tendency.