There is a problem of fault area identification of UHV tri-terminal hybrid HVDC transmission lines. Thus this paper proposes a fault zone identification method for three-terminal hybrid UHVDC transmission lines based on GRU. First, this paper analyzes amplitude-frequency characteristics of the DC power transfer function of the Kunbei and Longmen boundaries, and positive and negative difference of line mode power mutation in the T-zone. Also the difference of the fault characteristics when the fault occurs at different zones of three-terminal DC lines is found. Second, the wavelet transform is used to perform multi-scale wavelet decomposition of line mode power, the high frequency energy is extracted. Combined with line mode power mutation in the T-zone and the positive and negative DC power changes, the fault characteristics are formed and used as the input quantity of GRU. The fault area is used as the output quantity to construct the GRU fault area identification model. Then, the fault zone can be obtained by inputting fault characteristics to the trained GRU model. A large number of simulations verify that the method proposed has high accuracy and can withstand a transition resistance of 300 Ω.