This work aimed at studying the feasibility of calculating the coal–oxygen diffusion properties during the low temperature oxidation process of lignite so as to predict its spontaneous combustion process. Coal samples were oxidized in air ambient under different temperatures. Scanning Electron Microscope was used to indicate the surface morphology changes of oxidization. Then, based on fractal theory and flow characteristics, the fractal dimension of gas diffusion in the pore ways was calculated under different temperature. Considering pore size distribution, connectivity distribution and Fick diffusion mechanisms, the relationship between the gas diffusivity change with pore area fractal dimension and porosity was investigated, and multiple linear equation of the coal–oxygen diffusion coefficients and pore parameters was obtained. Comparison between the experimental data and model prediction verifies the validity of the model. The research provides a theoretical basis for the prediction model of coal–oxygen diffusion law. This work aimed at studying the feasibility of calculating the coal-oxygen diffusion properties during the low temperature oxidation process of lignite so as to predict its spontaneous combustion process. Coal samples were oxidized in air ambient under different temperatures. based on fractal theory and flow characteristics, the fractal dimension of gas diffusion in the pore ways was calculated under different temperature. diffusivity change with pore area fractal dimension and porosity was investigated, and multiple linear equation of the coal-oxygen diffusion coefficients and pore parameters was obtained. Comparison of the experimental data and model prediction verifies the validity of the model. for the pred iction model of coal-oxygen diffusion law.