In order to investigate the impact of the UHVDC protection logic module on the protective properties, according to protection hardware configuration, the recursive lagged effects of filter module in the signal processing circuit and the integral cumulative effects of the protection criterion export module are analyzed, the working principle of the module is described, and combined with the actual failure cases its impact on the protection characteristic is discussed and the optimization measures by modifying the internal configuration of the logic module to improve its operating characteristics are researched. It is verified by the previous fault waveforms playback, characteristics of logic element is improved, no protection misoperation occurs, which can improve the reliability of UHVDC protection. Some optimization measures has already been applied in engineering practice, it has certain reference value on the operation and maintenance in other HVDC system and the design of the subsequent project.