Abstract: Aiming at the problem of coal seam roof water disaster in arid and semi-arid mining areas in northwest China, in order to find out the distribution range of roof water channel in mining face, based on the whole space transient electromagnetic theory and the finite difference time domain algorithm, combined with the electrical characteristics of the strata in the demonstration mining area, a forward geoelectric model was established. The magnetic field response characteristics of different magnetic field components, different time and different detection angles of roof water channel in mining face were studied by numerical simulation, and the application experiment was carried out in the demonstration mining area of Xinjiang. The results show that the amplitude of the H_y magnetic field component corresponding to the normal direction of the wire frame is the largest, the magnetic field distribution trend is the simplest. The magnetic field intensity and attenuation gradient gradually decrease with time delay, and a secondary induction will be generated at the water channel of the roof, which will be used as the secondary field source to diffuse outward and attenuate. The H_y magnetic field component can identify the roof water channel, and the maximum effective detection elevation angle is 75°. The application experiment and later drilling in the demonstration mining area verify the feasibility and accuracy of the transient electromagnetic method in the detection of the roof water channel in the mining face.