Abstract: In order to provide theoretical support for the necessity of remote manual leakage tripping test, the distributed parameter circuit theory is applied to analyze the underground power supply system. By comparing and analyzing the AC equivalent circuit of actual selective leak detection protection device in situ, and with remote manual leakage, the test current is calculated and compared with the measured value. It is found that in situ test with smaller resistance about 3 kΩ to 5 kΩ and the distance test with larger resistance test of 11 kΩ can ensure the reliability of the selective leak detection protection device in the whole range of action resistance. By comparing and analyzing additional DC source leak detection protection device in the situ test and DC equivalent circuit for remote test, it is found that the transition process of the additional DC source leak detection protection device is obviously different from that of the remote test, and the difference of working environment between on-site test and remote test is analyzed. The conclusion is that the remote test is as necessary as the on-site test, and the reliability of the underground leakage protection system will be greatly improved by improving the remote test method and realizing the up-down and down-connected local test and remote test.