Abstract: The rich water in the mine floor is a major hidden danger that affects the safety production of coal mines. The use of geological radar for accurate identification of geological bodies and high-density electrical methods sensitive to water has the characteristics of high detection accuracy，accurate interpretation and high efficiency. Firstly，the basic principles of geological radar and high-density electrical method were analyzed，and then based on the forward modeling theory of GPR，the forward modeling of complete strata，dissolved pores and caves，karst caves and fractures were established，and the radar image characteristics of each model were analyzed. Based on the forward modeling theory of HDE，a complete formation，high-resistance，and low-resistance forward modeling models were established，and the inversion results were further given based on the analysis of the forward modeling response characteristics of the respective models. The results of numerical simulation show that GPR can identify the geological body according to image characteristics，and high-density electrical method can determine the water content according to the high-resistance and low-resistance response characteristics. Finally，the actual detection was carried out at the floor of the east wing of the fourth mining area of Hexi mine，and two water bearing anomalies were detected within 30 m below the bottom of the bottom of the floor. One was the water bearing fracture development zone，and the other was a water rich zone. The results show that the combined detection of mine GPR and high-density electrical method can accurately and effectively detect the water content of the floor.