The dissolution-precipitation behavior of zirconium dioxide (ZrO 2 ) in molten lithium fluoride-beryllium fluoride (LiF-BeF 2 , (2 : 1 mol, FLiBe)) eutectic salt at 873 K was studied. The results of the dissolution experiment showed that the saturated solubility of ZrO 2 in the FLiBe melt was 3.84 × 10 -3 mol kg -1 with equilibrium time of 6 h, and its corresponding apparent solubility product ( K ' sp ) was 3.40 × 10 -5 mol 3 kg -3 . The interaction between Zr(iv) and O 2- was studied by titrating lithium oxide (Li 2 O) into the FLiBe melt containing zirconium tetrafluoride (ZrF 4 ), and the concentration of residual Zr(iv) in the melt gradually decreased due to precipitate formation. The precipitate corresponded to ZrO 2 , as confirmed by the stoichiometric ratio and X-ray diffraction analysis. The K ' sp was 3.54 × 10 -5 mol 3 kg -3 , which was highly consistent with that from the dissolution experiment. The obtained K ' sp of ZrO 2 was in the same order of magnitude as that of uranium dioxide (UO 2 ), indicating that a considerable amount of ZrF 4 could inhibit the UO 2 formation when oxide contamination occurred in the melt containing ZrF 4 and uranium tetrafluoride (UF 4 ). Further oxide titration in the LiF-BeF 2 -ZrF 4 (5 mol%)-UF 4 (1.2 mol%) system showed that ZrO 2 was formed first with O 2- addition less than 1 mol kg -1 , and the precipitation of UO 2 began only after the O 2- addition reached 1 mol kg -1 and the precipitation of ZrO 2 decreased the ZrF 4 concentration to 0.72 mol kg -1 (3 mol%). Lastly, UO 2 and ZrO 2 coprecipitated with further O 2- addition of more than 1 mol kg -1 . The preferential formation of ZrO 2 effectively avoided the combination of UF 4 and O 2- . This study provides a solution for the control of UO 2 precipitation in molten salt reactors.