Abstract: In order to improve the accuracy of transient electromagnetic in advanced detection of goaf water, the goaf water models at different positions in front of the driving working face were established, and the three-dimensional FDTD method based on non-uniform grid was used for forward modeling, the response characteristics of transient electromagnetic field of goaf water under full-space conditions were analyzed with examples; the results show that the response curve of the transient electromagnetic field in the region with goaf water is obviously distorted, and the observation signal is mainly the attenuation information of electromagnetic field under the influence of goaf water; the closer the goaf water to the emitter, the earlier the response time of the magnetic field, the stronger the low resistance response of the magnetic field component in the normal direction; the application of multi-direction and multi-angle transient electromagnetic observation system is beneficial to locate the spatial position and distribution range of goaf water in the mine.