The physicochemical structure and spontaneous combustion characteristics of lignite change significantly after treatment with NaOH solution. Laboratory studies were undertaken to investigate the effect of different NaOH concentrations on the low-temperature (T < 200 degrees C) oxidation behavior of lignite. The experimental results showed that the low-temperature oxidation process of coal is divided into two stages by the apparent activation energy values, namely the slow oxidation stage and the rapid oxidation stage. In the first stage (T < 100 degrees C), the treatment with NaOH increased the coal pore volume by 8.3-38.7% and the porosity increased by 13.9-42.1%, resulting in the oxidation intensity of coal treated with NaOH being higher than that of raw coal due to the adsorption of more oxygen. In the second stage (T > 100 degrees C), high-concentration NaOH treatment remarkably reduced the content of reactive functional groups including aliphatic hydrocarbons, carboxyl groups, and carbonyl groups, thereby inhibiting the oxidation reaction behavior of coal. However, the low-concentration NaOH treatment had a catalytic effect on oxidation reaction by effectively weakening the hydrogen-bonding force of coal molecules and reducing the stability of the coal structure. Meanwhile, the crossing-point temperatures of coal treated with NaHCO3 and NaAc were 4.7 and 2.9 degrees C lower than those of raw coal, respectively, further indicating that the treatment with low-concentration alkali increases the spontaneous combustion propensity of coal.