The increasing speed of high-speed train and its traction power results in the increase in the grounding return current

the potential between train’s body and rail

and the aggravative electrical erosion to harm safe running of the train. In this study

field tests were conducted to measure the grounding return current of CRH380 series electric multiple units（EMUs）for the purpose of revealing the distribution laws of operational grounding current and protective grounding current

as well as the impact of EMUs grounding mode on traction return current. The results show that: 1)the waveforms of the operational and protective grounding currents are of almost same changing tendency

the maximum of the operational grounding current is 398.45 A

which accounts for72.29% of the total train body’s return current;and 2)The protective grounding current get its maximum on head and tail units of the train

which accounts for 66.68% of the total protective grounding return current. This study may provide a reference for the design of EMU grounding system.