The damping and voltage balancing components of thyristor-level in converter valves of high voltage DC transmission system need to be measured periodically, and a large number of thyristor-levels often makes it difficult to measure the component parameters accurately and conveniently by existing methods. This paper proposes a method to measure the parameters of damping and voltage balancing components, which can measure the component parameters accurately without removing connection wires for the entire converter valve. After analyzing the topology of the converter valve and the causes of measurement errors, the principle and procedure of the proposed measurement method are presented. The external circuit impedance is also regarded as a parameter to be solved, and the measurement of two adjacent thyristor stages in series is added, so that the established equations can be solved. Finally, the proposed method is verified by simulation analysis and prototype measurement respectively. The results show that the proposed method can measure the parameters of damping and voltage balancing components accurately without unwiring the converter valve.