Abstract: Coal resources in the lower formation of the North China type coalfield are seriously threatened by water in⁃ rush from confined aquifers such as thick limestone of middle Ordovician system and thin limestone of Taiyuan Forma⁃ tion. At present，it is an important means to eliminate the threat of floor water inrush and release coal resources by car⁃ rying out advanced regional grouting transformation of aquifers using horizontal directional drilling. However，due to the unclear diffusion law of grout in horizontal grouting hole of karst fissure aquifer on the floor and the lack of theoretical basis for determining key grouting parameters in grouting design and engineering practice，it is impossible to effective⁃ ly control the grouting process and ensure the grouting effect. Therefore，by means of laboratory test，theoretical deriva⁃ tion，numerical analysis，comparative verification and numerical simulation，this paper constructs a slurry diffu⁃ sion model of Newtonian fluid and viscotime⁃varying fluid in horizontal grouting hole of karst inclined fissure aquifer，and carries out comparative verification through model test and numerical simulation. The variation rules of grout diffu⁃ sion trace and diffusion distance of inclined fracture under different factors are calculated and analyzed. Research re⁃ sults show that the influence characteristics of slurry diffusion morphology and dip angle calculated by theoretical cal⁃ culation are consistent with the physical model test results and numerical simulation results of slurry diffusion in in⁃ clined fractures. In a single fracture of a Karst aquifer，under different grouting pressures，crack inclination angles (ex⁃ cluding 0°)，crack openings and grout water⁃cement ratios，the grout diffusion pattern is an approximate elliptical shape symmetrical along the central vertical line. The trace in the middle of the upper fissure shows slightly concave feature distribution，and the maximum and minimum grout diffusion distance appear at azimuth angles of 180° and 0° respectively. The range of grout diffusion trace increases with the increase of grouting pressure，fracture opening and grout water⁃cement ratio，and the increase range of grout diffusion trace is greater than that of grout at the bottom. The range of grout diffusion trace increases and decreases with the increase of fracture inclination angle in the lower and upper fractures respectively. Under the same conditions，the grout diffusion distance in the crack above the hori⁃ zontal grouting hole is larger than that in the bottom crack，and the distance shows a multiplier increase in the wide⁃ open crack scale.