Abstract: The spontaneous combustion is a slow low-temperature oxidation process. A lab-scale experiment for sponta- neous combustion propensity has been established. Basket heating method was used to investigate the oxidation process of four kinds of lignite and the kinetics of spontaneous combustion was determined. Thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy ( FTIR) were combined to study low-temperature oxidation reaction mechanism. It is found that moisture content can postpone the occurrence of spontaneous combustion without the influ- ence of intrinsic propensity. The spontaneous propensity is directly related with low-temperature oxidation reactivity:as temperature increases,the side chain will be oxidized into oxygenated groups,and more side chain and less aromatics is favorable to the propensity;the specific surface area determines oxygen absorption ability. The stronger of oxygen ab- sorption ability,the higher of spontaneous combustion propensity.