Kunliulong hybrid multi-terminal UHVDC project(KBL) is the first one of this kind project in the world. Its operation is more flexible than traditional two-terminal HVDC projects. Meanwhile it also increases the complexity of control and protection strategy. Abnormal action has occurred several times since KBL was put into operation. So the reliability of this "first set" control and protection system needs to be analyzed and improved. This paper first illustrates the "6·9" valve-controlled triggering abnormal events of KBL by comprehensively sorting out the control and protection configuration and DC response. The valve group triggering abnormal detection and protection function is proposed and put into application. This strategy can detect the valve control pulse loss or pulse delay fault accurately and fast and improve the ability of risk identification and resistance for DC control and protection system to abnormal valve group triggering in abnormal working conditions. It can also effectively improve the reliability and stability of KBL operation, and the research results can provide reference and guidance for the functional design of control and protection system of subsequent hybrid multi-terminal UHVDC project.