NOVELTY - Sulfur and sodium are arranged around a sodium ion conductive solid electrolyte, as positive and negative electrode active materials, respectively, for operating sodium-sulfur battery. A multi-sulfided sodium is produced in the positive electrode active material during discharging and the multi-sulfided sodium is changed to sulfur during charging, during the operation of the battery.    USE - For operating sodium-sulfur battery for emergency use.    ADVANTAGE - The sodium sulfur battery is operated properly in the common operation mode and emergency operation mode, compared with conventional operating method. The operation method suppresses necessary heat energy to temperature set up during running. The operational efficiency is improved. Corrosion of battery consumption elements such as battery jar are reduced by lowering the battery temperature from conventional battery temperature. The battery has improved durability for a longer period of times.    DETAILED DESCRIPTION - Sulfur and sodium are arranged around a sodium ion conductive solid electrolyte, as positive and negative electrode active materials, respectively, for operating sodium-sulfur battery. A multi-sulfided sodium is produced in the positive electrode active material during discharging and the multi-sulfided sodium is changed to sulfur during charging, during the operation of the battery. An equal load is applied and the battery discharges in a time zone which does not have surplus power in supply of electric power and charges in time zone which has surplus power in supply of electric power, in the common operation mode. A non-stop electrification of a load is implemented during emergency use operation mode, which discharges during power failure and charges while resuming electric power supply. The battery temperature is set up more than melting point of disodium pentasulfide and in a standby state in which the discharge after completion of charging of each operation mode is possible below the melting point of disodium tetrasulfide. The battery temperature of discharge final stage in common operation mode and in emergency use operation mode are set to more than the melting point of disodium pentasulfide and disodium tetrasulfide, respectively.