In order to accurately analyze the evolution law of spontaneous combustion ' three zones ' in goaf during the mining process of low metamorphic thick coal seam, the PFC-Fluent method was used to simulate the caving and voidage distribution of overlying strata in goaf by using PFC particle flow simulation software. The obtained voidage distribution data were imported into Fluent numerical simulation software. Through the established goaf model, the oxygen concentration was used as the basis for the division of ' three zones ' in coal spontaneous combustion goaf. The range of spontaneous combustion ' three zones ' in goaf is obtained and compared with field measurement. The results show that the ' three zones ' of spontaneous combustion measured by the combination of PFC-Fluent method is close to the field measurement, and the minimum advancing speed of the working face is calculated to be 0.69 m / d, which is used to guide the coal mine production work. It has certain theoretical guidance and practical application significance for preventing spontaneous combustion in goaf.