Abstract: Fast switching fault current limiter is one of the effective schemes to limit short-circuit currents. In this study, a multi-fracture series tank-type fast switch suitable for 500 kV fault current limiter is proposed, in which gas insulated metal enclosed structure and vacuum insulated fracture are adopted. The operating mechanism adopts electromagnetic repulsion mechanism, three-dimensional finite element simulation and optimization are performed to effectively improve the output efficiency of repulsion mechanism, and the average opening speed is greater than 5 m/s. In terms of ground insulation, the insulation tests for electric field simulation optimization machine of fracture insulation shielding structure are carried out, and the maximum field strength after structural optimization is 18 kV/mm. In terms of inter terminal insulation, the stray capacitance simulation, equal-voltage effect simulation and test verification of the whole machine are carried out. By configuring the voltage equalizing capacitor, the non-equal-voltage coefficient is limited to less than 1.24. Finally, the prototype of the whole machine is built and the short-circuit breaking test is carried out. The test results show that the tank-type fast switch has the ability to quickly break 50 kA current, and the total breaking time is less than 15 ms.