Abstract: Directional regional grouting to transform aquifers is one of the effective ways to prevent and control mine water hazards. In order to study the diffusion law of grouting slurry in directional areas, a three-dimensional simulation test system for directional area grouting has been independently developed. The system is mainly composed of test bench, grouting system, water injection system, data monitoring and other subsystems, which can realize directional drilling grouting simulation, three-dimensional slurry diffusion simulation, high pressure water simulation and regional grouting simulation. The system can independently control the grouting hole unit to achieve porous and multi sequence grouting. With the help of six grouting holes, the slurry flow process is simulated under various parameters such as different grouting pressure, slurry viscosity, grouting rate, and water cement ratio. It can also achieve real-time monitoring of the slurry diffusion process in dynamic/static (high) water pressure environments. The paper takes the simulated naked hole lengths of 200 mm, 250 mm, and 300 mm as the research objects, and preliminarily explores the characteristics and effects of slurry diffusion in naked hole grouting under directional grouting. The study found that: in the case where only the naked hole length is a variable, the slurry diffusion range does not synchronously increase linearly with the linear increase of naked hole length; The slurry stone body of the short open hole is cylindrical with the drilling open hole as the axis, while the slurry stone body of the long open hole is circular with the drilling open hole as the axis; Increasing the same length of the bare hole results in a larger difference in the diffusion range of the slurry at both ends of the bare hole. At the same time, the more pressure loss there is, the smaller the diffusion distance of the slurry. Comparing the diffusion radius of the slurry obtained from the experiment with that calculated by the Maag formula, the difference between the two values is only 2.8% when the length of the grouting open hole is 200 mm. The experimental results comply with the Maag spherical diffusion theory and verified the scientificity and rationality of this experimental system.