The surface tensions of REF3-LiF (RE = La and Nd) molten salts (REF3 mol% = 20-40%) were measured using the slide method over the temperature range1223-1423 K which was specifically chosen for meeting the actual electrolysis temperature (about 1323 K). The temperature and composition dependences of the surface tensions were investigated. The results showed that the surface tension decreased linearly with the increasing of temperature and increased nonlinearly with the increasing mole fraction of REF3. At 1323 K (near the practical electrolysis temperature), the surface tension of REF3-LiF-RE2O3 molten salts firstly increased with the increasing RE2O3 and reached the maximum value near the solubility of RE2O3 (2-3 g) in REF3-LiF molten salts, and then decreased with the continuously adding RE2O3. The accurate knowledge of the surface tension factor of RE2O3 can be useful for well understanding the solubilizing mechanisms of RE2O3 in REF3-LiF molten salts system. Results of this study well supplemented the experimental data of physiochemical property on surface tension of rare earth fluoride electrolytes. (C) 2016 Elsevier B.V. All rights reserved.