Abstract:The galloping of transmission lines in some sections of ± 500 kV GaoZhao HVDC transmission line is very serious, which causes the damage of the conductor and fitting because of the periodic stresses produced by galloping. In order to decrease the damage produced by the galloping of transmission lines,± 500 kV phase - to - phase composite spacer has been developed and applied in ± 500 kV GaoZhao HVDC project,which increases the anti - swing and anti - galloping ability of lines. It is the new phase - to - phase composite spacer developed in China for the first time,which is tested by some electrical and mechanical research and analysis. This kind of composite spacer has passed all the technical tests covered mechanical and electrical requirements and has been used in ± 500 kV GaoZhao HVDC project. It not only provides the solution for the galloping of transmission lines in ± 500 kV GaoZhao HVDC project,but also provides the technical support to solve the galloping and swing of conductors in EHV and UHV transmission lines.