Abstract: The main technical means for preventing and controlling karst water damage in the coal seam floor of North China type coal fields are grouting transformation of the water-bearing rock layer. Currently, the main method for testing the grouting effect is to analyze the lithological features before and after grouting. There is a lack of tracking and dynamic monitoring of the entire grouting process, making it difficult to accurately evaluate the grouting effect. In order to solve the above problems, an inter hole resistivity monitoring system is introduced to monitor the entire process of resistivity changes in grouting transformed rock layers, in order to achieve precise detection of the slurry diffusion range. Firstly, an improved electrode and cable device is used to place the resistivity monitoring system in a long directional borehole on the coal seam floor, achieving resistivity monitoring between boreholes. Secondly, a geological model of slurry diffusion is constructed, and the simulated data is processed and interpreted using three-dimensional resistivity inversion. Finally, engineering tests are conducted on the inter hole resistivity monitoring of the entire grouting process at the injection layer underground in the coal mine. The simulation results indicate that inter hole resistivity monitoring can identify the diffusion range of slurry anomalies. Based on the trend of resistivity changes over time, the diffusion range of slurry can be inferred. As the slurry gradually diffuses, the range of anomalous areas gradually increases and the intensity of anomalies gradually increases. The engineering test results show that the resistivity monitoring system is arranged on the grouting layer through drilling for dynamic monitoring. After three-dimensional inversion imaging of the monitoring data, the features of resistivity changes in the grouting layer caused by slurry diffusion can be successfully captured. It provides a feasible technical solution for detecting the grouting effect in coal mines.