The utility model provides a 400kV post insulator bus mounting structure of an extra-high voltage converter station. The device comprises a first 400kV bus (4), a cross aluminum stranded ring fitting(5) and a second 400kV bus (7), the first 400kV bus (4) is supported by the first 400kV post insulator (1); the second 400kV bus (7) is supported by a second 400kV post insulator (6); the cross aluminum stranded ring fitting (5) is arranged between the first 400kV post insulator (1) and the second 400kV post insulator (6), and two opposite ends of the cross aluminum stranded ring fitting (5) respectively form a conductive connection structure with the first 400kV bus (4) and the second 400kV bus (7). According to the utility model, the displacement requirement and the electrical connection requirement between power equipment under the earthquake working condition can be well satisfied, the anti-seismic property of the 400kV post insulator body and the bus connection loop thereof can be effectively improved, and the 400kV post insulator bus connection loop has the outstanding advantages of ensuring the stability and the reliability of the 400kV post insulator bus loop and the like.