Abstract: The differences in grounding methods of voltage transformer secondary circuits between domestic and oversea are introduced. For domestic projects, the secondary circuit of voltage transformers with electrical connection can only be grounded at one point in the electric protection room, while for foreign projects, grounding in the switch yard marshaling box is required. By analyzing and comparing the advantages and disadvantages of the two grounding methods of the voltage transformer secondary circuit and whether the neutral line is involved in voltage switching/parallel operation, it is shown that the best grounding method for the voltage transformer secondary circuit is one point grounding in the marshaling box. The voltage transformer secondary circuit grounding improvement program is proposed, and it is suggested to optimize or modify the provision of "the neutral line of voltage transformer should not be connected to breaker or fuse, etc. that may be disconnected" in the domestic standard.