The invention relates to the technical field of new energy, in particular to an electric energy storage device of a salt cavern flow battery, which comprises: an air bag that is located in a salt cavern, wherein the salt cavern is located under the ground surface, brine is stored in the salt cavern, and electrolyte is stored in the air bag; a second pipeline with one end connected with the air bag, and the other end of the second pipeline is located on the ground surface, and the second pipeline is used for injecting the electrolyte into the air bag; a first pipeline that is nested outside thesecond pipeline, wherein one end of the first pipeline is connected with a shaft inlet of the salt cavern, the other end of the first pipeline is positioned above the ground surface, and the first pipeline is used for discharging the brine from the salt cavern. By adopting the electric energy storage device, the electrolyte is isolated from saturated brine in the salt cavern, underground water resources are not polluted, and meanwhile, the original electrolyte does not need to be replaced, so that the energy consumption can be effectively reduced.