Due to the high frequency change of the membership relationship of the substation-line-transformer, the relationship of the substation-line-transformer is complex. This paper designs a method based on FM-EEMD signal decomposition to identify the line-dependent relationship. The method makes use of the characteristics of the carrier signal, such as small shunt ratio at the low-voltage side load and other branches, and large shunt ra- tio at the medium-voltage side of the transformer of the correct branch. By injecting a carrier signal of a certain frequency into the 0.4KV side, the strength of the carrier signal at medium-voltage side is detected to identify the substation-line-transformer relationship. In this paper, the signal of the medium voltage side is decomposed by the FM-EEMD method and the line change relationship is identified by analyzing the carrier signal which is obtained by FM-EEMD. Simulation and experiments show that this method can extract carrier signals effectively.