Conventional transient electromagnetic underground detection requires ground processing, which takes a long time and lags behind the guidance of mine production. Real-time transient electromagnetic detection technology can see the detection results quickly and intuitively and provide sufficient time window for drilling. In order to obtain the physical characteristics of No.9-805 Face in Pangpangta Coal Mine, the real-time transient electromagnetic parameter test was carried out according to the idea from unknown to known. The water accumulation in No.5-109 goaf in the upper part of No.9-805 Face was detected, and the data was processed in real time. The apparent resistivity contour map was drawn, and the abnormal area of water accumulation was delineated. After drilling verification, the accurate underground water accumulation area was finally determined and the drainage was carried out, which verified the correctness of the real-time transient electromagnetic detection parameters and guided the safe mining of the working face.