The purpose of high-temperature superconducting (HTS) cables as the transmission conductor in a high-voltage dc transmission system is mainly to reduce the Joule losses arising from the power transmission process. However, the harmonic currents generated from the switching behavior of the voltage source converters result in power loss in the HTS dc power cable. The cable loss characteristic should be analyzed in terms of its practical applications. In this paper, the harmonic currents characteristics were analyzed in both steady and transient state. An HTS dc cable model was also developed using the finite elements method to examine its loss characteristics. The results showed that the harmonic loss of the HTS dc model cable depends on the properties of the voltage source converters, the operating dc current level, and the ac system conditions. This work will be useful in studying the loss analysis of a real HTS dc power cable.