Abstract: The ±1100 kV is globally the highest voltage grade in DC transmission. Studying the typical clearance discharge characteristics of 1100 kV converter station and giving the recommended value of its air clearance are of great significance for reasonably determining the design of converter station and ensuring the reliable operation of the project. In this paper, for three typical voltage-sharing ball-to-ground clearances（the diameter of the voltage-sharing ball is 1.1 m～ 2.0 m and the clearance distance is 3.0 m～10.0 m）, switching impulse discharge tests were conducted, and 50% discharge voltage values were obtained. The discharge characteristic curve of the large-size and long-clearance distance voltage-sharing ball-to-plate clearance was obtained by regression, and the equation of critical diameter of voltage-sharing ball was proposed. The influences of factors like adjacent walls and post insulators in converter station on the discharge voltage of large-size ball-to-plate clearance were experimentally studied, and the corresponding variation coefficients were obtained. Finally, according to the insulation level of typical clearances of converter stations for ±1100 kV projects, the values like minimum clearance distance and typical clearance coefficient for typical ball-to-plate clearances were recommended. The research results had been applied to determine the clearances for valve halls and indoor DC fields in converter station of ±1100 kV UHV projects.