Abstract: Curtain grouting has gradually become one of the main technical means for prevention and control of mine water damage. To solve the layout problem of grouting hole spacing in curtain engineering,the physical properties of the grouting material were obtained through laboratory experiments,and using COMSOL numerical software,the numerical model of pure liquid cement slurry diffusion in curtain grouting of underground aquifer was established. The mechanism of grout diffusion in curtain grouting engineering of underground aquifer was studied. Research results indicates that the larger the water-cement ratio of pure liquid cement slurry,the longer the setting time of the slurry,the greater the viscosity,and the smaller the calculus rate and compressive strength; the diffusion form of curtain grouting for pure liquid cement slurry in the underground aquifer is circular diffusion centered on grouting hole,the slurry diffusion radius increases with the increase of grouting time. The average diffusion radius of the stabilized slurry is 10.22 m,and the distance of slurry diffusion reached 20.44 m. The theoretical and numerical calculation results for the diffusion radius of pure liquid cement slurry are relatively consistent. The error between theoretical solution and numerical solution is less than 5%. It shows that the established numerical model is reliable to study the slurry diffusion in curtain grouting. According to the results of numerical simulation and theoretical calculation,the grouting hole spacing in curtain grouting process is selected as 20 m,and a curtain wall with an effective width of about 40 m is built with two rows of staggered holes to block the recharge of the mine from the aquifer outside the curtain wall. After the curtain wall is constructed,the core containing slurry stone body is obtained through inspection holes,and its compressive strength is 11.2 MPa,which can meet strength requirements of curtain wall construction. It is proved that the grouting hole spacing in curtain grouting project is reasonable.