Simulation and experiment studies focusing on the fast mechanical switch in hybrid HVDC circuit breaker as the critical component applied to ±160 kV Nan’ao VSC-MTDC project are carried out. The fast mechanical switch with two 80 kV fractures connected in series and with SF₆ as insulating media is studied. Then electric calculation of each 80 kV fracture is performed with Ansoft Maxwell. The result shows that each fracture can withstand 80 kV DC voltage with 15 mm opening stroke between the static and movable contact. In addition, the feasibility of the fast mechanical switch using the electromagnetic repulsion mechanism as fracture is studied and the experimental prototype is built up. It is verified by experiment that this fast mechanical switch can be used to drive from its closing state to opening state within approximately 3 ms.