Abstract: In order to accurately predict the diffusion characteristics of cement mortar grouting and sealing slurry in gas drainage boreholes, and considering the infl uence of time-dependent viscosity of slurry on the diffusion of cement mortar and the effect of stress on coal deformation,a time-dependent viscosity diffusion model of cement mortar grouting based on the theory of grouting fluid-solid coupling is presented in this study. The time-dependent viscosity diffusion model of the sealing viscos ity of the drilling cement mortar,using COMSOL numerical simulation to study the distribution characteristics of the grout diffusion under different grouting pressures and considering the influence of the time-dependent viscosity of the grout on the results of the grouting diffusion range ,and the field test verification is carried out in Xinyi C oal Mine. The research results show that:①The time-dependent diffusion model presented in this study comprehensively considers the influence of slurry viscosity time -dependent and grouting pressure on coal deformation,which can more comprehensively predict the slurry diffusion characteristics during grouting;②When the water-C ement ratio is 0.9,the cement slurry grouting effect can be achieved and the corresponding cement slurry viscosity gradually shows an exponential growth with time;③ he time-dependent viscosity characteristic of cement mortar slurry plays a direct effect on the spreading range of the slurry. Considering the time-dependent viscosity of the slurry,the diffusion range is smaller than when the viscosity of the slurry is considered as a constant slurry;④The actual verification effect of the cement mortar diffu sion model with the time-dependent viscosity of the gas drainage borehole shows that the optimal sealing grouting pressure is 1.4 MPa.The research results can provid e theoretical support for further optimizing the cement mortar grouting sealing scheme and improving the quality of gas drainage borehole sealing.