The invention relates to an accurate sampling method for a rare earth molten salt electrolytic cell. The method is characterized in that: a rod-shaped sampling device with a sealing sample compartment is employed for sampling in a reaction zone of the rare earth electrolytic cell, and is able to completely take out the lump molten salt in the compartment. The method has the advantage that the molten salt captured in the sampling process is not disturbed by the outside molten salt. The method takes full usage of the characteristics of high melting point of the molten salt, so that the molten salted is cooled, solidified and taken out in an entire block and analyzed; and the method avoids the dumping condensation of a low-temperature phase on the vessel surface in the dumping process, and the influence of the precision of sampling. The sampling device is easy to operate and has good sealing performance; with the help of a lower plug, the sampling device can quickly take out the complete sample in the compartment, so as to realize high sampling efficiency; and the sampling of a next electrolytic cell can proceed immediately.