Abstract: Based on the extreme challenge of environment in ultra-deep waters,the requirements on the BOP stack and its control system are very high in order to ensure secure operation.In view of the current situation,an unified standard for ultra-deep water BOP stack is still unavailable in the oil industry and the research and development of BOP stack is also in its infancy in China.An enhanced configuration was put forward through analyzing functions of the subsea BOP and its control system.Different from the present technical standard and the configuration of HYSY981 ultra-deep water drilling unit,the capacity of shear ram is improved and the backup and special control system are compulsory items in this configuration,which improves the safety and reliability of ultra-deep water drilling operation significantly.