Abstract: After the mining of the coal mining face is completed, the internal environment of the goaf formed is complex, and it is very difficult to accurately detect the range of accumulated water and calculate the amount of accumulated water. The traditional manual calculation method refers to the contour lines of the coal seam floor and the range of the goaf, relying only on information such as the length and width of the working face and the mining thickness of the coal seam. There are significant human generalization factors. The calculation results are difficult to reflect the true situation of water volume in the water accumulated goaf, and the calculation workload is large and the accuracy of the calculation results is low. It is impossible to calculate the accumulated water volume and the extent of water accumulation in real time based on hydrological monitoring data, and it is also impossible to dynamically analyze the threat of water accumulation changes to safe production. As a result, the hazard sources and dangers in the goaf cannot be obtained in a timely and accurate manner, leading to frequent water inrushes in the old goaf. In order to grasp the range of water accumulation in goaf in real time, accurately calculate the amount of accumulated water and achieve real-time early warning for the mining safety of adjacent working faces, etc., based on the three-dimensional model of the base of the goaf and the monitoring data of the water level of accumulated water, a method for dynamically simulating the water accumulation area in the goaf is proposed around the on-site engineering practice of real-time monitoring, real-time simulation and real-time evaluation of water accumulation in the goaf. Firstly, the base model of the goaf is constructed through the data of coal seam control points. The three-dimensional water surface model is dynamically generated using the water level monitoring elevation data. After cutting the water surface model from the base model of the goaf, the three-dimensional model of the accumulated water body is further constructed. Secondly, the voxelization algorithm is adopted to accurately calculate the range and volume of the accumulated water body, and the accumulated water volume is calculated in combination with the water filling coefficient. Finally, the three-dimensional model of the accumulated water body in the goaf is dynamically displayed in the 3D engine, and the key data such as the water level and water volume of the goaf are dynamically pushed to be displayed in the software panel. The practice in Shendong Mining Area shows that the dynamic simulation method of the water accumulation area in the mined-out area has improved the accuracy and timeliness of the calculation and simulation of water accumulation in the mined-out area, providing precise spatial position information of the accumulated water body for the design of water exploration and drainage projects and the exploration of concealed disaster-causing factors.