Abstract: To investigate the main controlling factors and diffusion characteristics of long-distance slurry migration in horizontal boreholes at the top of the Ordovician limestone,this study employed multi-field coupled numerical simulations and orthogonal experimental design. The factors influencing slurry migration were classified into three categories:external groating driving forces,slurry properties,and formation characteristics. The individual effects of five factors—grouting pressure (A),slurry density (B),slurry dynamic viscosity (C),permeability (D),and porosity (E) of the porous medium—on slurry migration were systematically analyzed. Field tracer tests were also conducted to measure the horizontal and vertical diffusion ranges of the slurry within the karstic medium atop the Ordovician limestone. The results show that the factors rank in order of influence on slurry diffusion as D > E > A > C > B. Formation characteristics are the dominant factor group constraining the diffusion range,followed by external driving forces and slurry properties. Tracer tests revealed that the horizontal diffusion range exceeds 45 m,the vertical upward range exceeds 30 m,and the vertical downward range exceeds 35 m,which are consistent with the numerical simulation results. The tracer tests provided measured data on slurry migration and diffusion ranges for surface directional horizontal grouting boreholes; together with the numerical simulations, these data offer a basis and reference for selecting grouting horizons, determining branch-hole spacing,and evaluating the effectiveness of advanced regional floor water hazard control.