In order to accurately calculate corona loss from the bare bundled conductors of HVDC transmission lines, considering the uneven distribution of sub-surface electric field caused by interactions between the sub-conductor, different corona onset voltage and corona loss differences in different positions as sub-conductor, the authors propose a more accurate method of calculating of bipolar corona loss from the bare bundled conductors of HVDC transmission lines by analyzing mechanism under the corona, according to the condition of gas self-sustaining discharge to decide corona onset voltag. The method is applied to the synthetic electric field of ±800 kV to verify its effectiveness. The results show that the corona loss is the most serious outside of sub-surface distribution of wire round and lighter inside even without any corona loss. Each pole’s losses are mainly concentrated in three sub-lines inside of the wire. Finally, analysis the affection of ± 800 kV line parameters on corona loss. The results show that sub-conductor radius and pole pitch have obviously impact on the corona loss and they are the main factors. They should be given priority in engineering design.