Abstract: Equivalent circuit method was adopted to design a small NaK thermal vacuum electromagnetic pump of which the rated working temperature was 500 ℃, rated flow rate was 11 m³/h and rated head was 30 kPa. The ATC-S_NaK facility of China Institute of Atomic Energy was used to obtain the operating characteristic curves of the electromagnetic pump. The influence of working medium temperature, power and operating frequency on the running characteristics of the pump was analyzed. The results show that the optimum operating frequency of the pump is related to the working medium temperature of the NaK, which is meaningful for the design of the pump and development of the operating procedure.