Water zones adjacent to coal seams seriously threat coal mine's safety in production. In the mining process along No. 1171 roadway, water content significantly increased in the front. In order to avoid the water disaster, the authors carried out measurement on the whole working face. Transient electromagnetic measurement was chosen, and ground and underground coal mine transient electromagnetic combined exploration was conducted in water-rich area. The flood range was controlled in plane by ground transient electromagnetic method, and the underground water-rich area was delineated by using downhole detection method, so as to guide further pumping and drainage work and reduce the possibility of water damage. The results of the ground and underground transient electromagnetic fields are the same, and the results of the water-rich areas are also he same. The combined detection reduces the possibility of multi-solution of geophysical prospecting data and thus can greatly improve the exploration precision. It can improve the reliability of the coal mine prevention and control.