Abstract: Grouting modification and reinforcement technology is an effective way to control the stability of fractured coal surrounding rock. Accurate prediction of infiltration and diffusion law of grouting slurry in fractured coal is of great significance for scientific evaluation of grouting effect. The influence of heterogeneous distribution of fractures in coal is not taken into account in the traditional grouting seepage diffusion model, which results in a large error between the prediction results and the monitoring data. In this paper, based on the coal mining and excavation project of No.3-Biangle 091 tunnel in Jingfang Coal Industry of Shanxie, the identification method of coal seam rate based on digital photography and digital image processing technology is proposed, and the heterogeneity characterization model of coal seam based on Weibull distribution is established. A numerical calculation model of grouting grout permeability and diffusion was established by using multi-physical field coupling software COMSOL, which considered the heterogeneity distribution of coal fissures. The influence of coal average fracture rate, fracture distribution homogeneity index and other parameters on grout diffusion distance and grouting pressure distribution in coal was studied. The results show that: When the average fracture rate is higher and the fracture distribution homogeneity index is higher, the grout pressure is higher and the permeability and diffusion rate of grout is faster. However, when the fracture distribution homogeneity index reaches a certain degree, the fracture rate distribution in the model tends to be uniform and has little influence on the permeability and diffusion results of grout. Compared with the traditional model (homogeneous model), the permeability and diffusion distance predicted by the model (heterogeneous model) in this paper is reduced by 16.9%, which is consistent with the law of uneven permeability and diffusion of grout in practical engineering, and has a certain theoretical significance for guiding the grouting design of fractured coal.