Abstract: Aiming at the problem of harmonic current amplification in bipolar HVDC transmission lines, we propose a quantitative calculation method of harmonic current transfer coefficient of HVDC line on the basis of analyzing the distribution parameters of lines, which can be used to evaluate the amplification level of harmonic current. Firstly, based on the coupling relationship of multi-conductor lines and the structure of bipolar overhead lines, the harmonic impedance model of overhead line is established. Secondly, the analytical formula of the harmonic current transfer is obtained and the main influence factors of harmonic amplification is analyzed. Then, based on the wave propagation of the transmission line, the transmission regularities of harmonic currents are explored. Finally, combined with the parameters of a HVDC transmission project, under the three-terminal operation mode with non-uniform lines, the accuracy of the proposed harmonic current calculation method is verified in the PSCAD simulation platform.