A short-circuit test method for a medium-
voltage bus of an EMU, which is characterized in that it includes the following steps: 1) The 
train is provided with multiple auxiliary 
converters, each auxiliary converter is connected in parallel for output, and N 
coupling switches are set on the medium-
voltage bus, and the normal operation is  In the 
closed state, ensure that the medium-
voltage bus runs through all columns; 2) Once a short-circuit fault occurs in the vehicle, first confirm whether it is an internal fault in the auxiliary converter to reduce the scope of the fault; 3) If there is no short-circuit fault in the auxiliary converter, the vehicle will  Start the external short-circuit 
test program, open N 
coupling switches, divide the medium-voltage bus into N+1 sections, and then put in the auxiliary 
converters to judge the faulty bus section; 4) After confirming the faulty bus section, open the adjacent  1 or 2 
coupling switches, and the non-adjacent coupling switches are closed to ensure the normal operation of medium voltage loads in the bus section without 
short circuit.  The invention can refine the short-circuit fault point, reduce the range of fault influence, even avoid the fault influence, and maintain the operation of the vehicle to the greatest extent.