Through the oxidation of coal at low temperatures and the resulting petrographic analysis, this study aims to predict spontaneous combustion, which has emerged as an industrial problem. Low-temperature oxidation analysis and the corresponding petrographic characteristics of four different coals treated under low temperatures of 25, 50, and 75 °C, which was set as the reactor temperature, were investigated. Low-temperature oxidation experiments designed at Pusan National University, based on papers related to low-temperature experiments, were conducted to analyze the constant of oxidation reactions. The petrographic characteristics of the coals were analyzed using a coal petrographic microscope spectrophotometer for determining their vitrinite reflectance and morphology, and the coals were extracted after the low-temperature oxidation experiments. After these analyses, vitrinite reflectance changed, and the normalized k, which is the difference between the constant of reaction from 25 °C to (the setting temperatures of) 50 and 75 °C, was also calculated. By comparing the oxidation rates of the coals and the corresponding petrographic analyses, the cause of spontaneous combustion can be deduced and a prediction can be made about which coal burns most efficiently at a low temperature.