Abstract: Though some achievements concerning the transient electromagnetic method for advance water probing in tunnels have been made, further study is needed regarding the transient electromagnetic effect mechanism on a tunnel as a whole. By means of a physical model test, the physical similarity criteria were determined and the similar materials were selected. The relationships between brine conductivity, concentration, and temperature were studied using a self-made experimental apparatus. The transmitter and receiver coils were designed and transformed. The model test platform with whole space transient electromagnetic methods was set up, and many groups of tests were conducted that verified the correctness of the numerical simulation results.