Abstract: Study of the electromagnetic environment of UHVDC transmission lines is very important for construction of UHVDC transmission lines in China. Several methods, including charge simulation method, finite element method and formula of CISPR and EPRI, are used to calculate the relevant parameters, such as total electric field, ion current density, magnetic field intensity, radio interference and audible noise. The calculation is based on the limits of electromagnetic environment of ±1 100 kV UHVDC transmission lines and the given initial conditions. The research result shows that the audible noise is the controlling factor for selecting conductor types. Various conductor types are recommended according to different pole intervals and altitudes in this paper and the minimum ground clearance of different conductor types are also given.