Common water disasters in coal mines included roof water hazards, floor water disasters, old empty water disasters, fault and collapse column water hazards and so on, old empty water was the main cause of mine flood accidents among them. The featur of goaf water was large hydraulic pressure which became ferocious and disruptive once digging through, but the duration of water gushing was short and easy to drain. In roadway construction process, using geophysical prospecting and drilling methods to detect goaf water effectively was an important work for water disaster prevention and control in coal mine, which made a difference in safety production. The detecting process of goaf water in western 2102 working face was taken as an example in this paper, effectiveness of transient electromagetic technique to detect goaf water and its significance in the roadway construction process were introduced.