The automatic sequence control function of valve group state transition is one of the most basic control functions for DC system. The successful auto-completion of valve group state transition is also the important inspection index of working stability for DC control system. This paper introduced the implementation process of valve group state transition in Yunnan-Guangdong DC transmission project, analyzed the irrationality of current circuits design and its hidden danger. The solution method proposed has been successfully applied in Yunnan-Guangdong and Nuozhadu DC transmission projects, which has certain practical significance to the steady operation of UHVDC systems.