The pyroprocessing technology of spent fuel is promise because of its advantages compared with the wet-processing technology; however, the development of pyroprocessing technology depends on the availability of basic physical chemistry properties for the relevant molten salt mixtures. In this work, the first principles molecular dynamics (FPMD) simulation is applied to the evaluation of redox potential of tetravalent actinides (Pa4+, U4+, and Np4+) in molten LiCl-KCl (ClLiK) eutectic. The reduction energetics, referenced to Th4+, is analyzed in terms of vertical substitution and relaxation, and satisfactory agreement is reached between our FPMD evaluations and experimental results reported in literatures. (C) 2018 Elsevier Ltd. All rights reserved.