In order to improve the reliability of ultra high voltage direct current（UHVDC） transmission system， the structure and configuration design for UHVDC control system are discussed. Based on the experiences of conventional HVDC control system， three structure and configuration design schemes for UHVDC control system are presented and compared in computer number， load rate， reliability， information interchange amount and system complexity. The optimum design scheme of separating of bipolar/pole control and valve groups control is proposed. By effective layering of control system and reasonable distributing of software， the coupling among subsystems is decreased and the reliability is improved. The scheme is verified by the prototype of UHVDC control system. The research results would be used in UHVDC projects to meet the requirements of the UHVDC.