Abstract: The high-voltage lead exit in conventional UHV AC transformers is installed in a compact ascending flanged base external to the tank. Due to the semi-enclosed and narrow space of the elevated seat, once an arc fault occurs in the lead exit, the accumulation of impact pressure in the elevated seat is more serious than the fault of tank, resulting in a higher risk of seat tearing and explosion. Under extreme faults, a large amount of insulating oil overflows and burns. In order to improve the explosion-proof capability of UHV AC transformers, this paper proposes a design scheme for transformer based on direct output structure. Optimization design was carried out for the oil-paper insulation structure of the direct lead exit. 1 000 kV direct lead exit device is developed, and the insulation margin, vibration, and impact tests verified that the lead exit has insulation reliability and mechanical stability. A prototype of UHV transformer using direct lead exit structure has been developed and passed the type tests. Simulation shows that the indirect tank outlet structure has a high risk of structural failure when a 20 MJ arc occurs, while the direct outlet can withstand a 50 MJ arc energy. Transformer using embedded lead exit have better anti explosion performance than indirect output devices.