This study evaluates nuclear characteristics of molten salt, namely LiF-NaF-BeF_2 (FLiNaBe), from the viewpoint of its application to a liquid blanket system in a fusion reactor. Monte Carlo numerical simulations using MVP-2.0 with JENDL-4.0 data library and time-dependent nuclear transmutation analysis are carried out to evaluate tritium breeding ratio, change in the compositions of the molten salt. Induced radioactivity of Na contained in FLiNaBe is also evaluated. The results of the numerical analysis reveal that the thermophysical properties of FLiNaBe should vary because the compositions of the molten salt definitely change due to the fusion plasma neutron during power plant operation.