Abstract: Based on industry practise, the effects of the proportion of molten salt of fluoride used in 10 KA neodymium molten electrolysis on electrical current efficiency, bath age and carbon content of neodymium were studied.It is pointed out that the proportion of fluoride molten salt is the foundation of the whole technics, which directly affects the primary technique and economics index. It hold 80 %-82 % electrical current efficiency in the long term industry production.