Abstract: The grid-connected consumption of "green and low-carbon" new energy such as large-scale wind power and new photovoltaic power urgently needs the development and research on new flexible DC transmission technology and equipment. On the basis of the test and demonstration project of Zhangbei DC power transmission, this paper systematically studies the core equipment of hybrid DC circuit breaker. According to the working principle of hybrid DC circuit breaker and the performance requirements of fast mechanical switch, the high-voltage fast mechanical switch is proposed. Through the finite element simulation of the dynamic characteristics of fast mechanical switch, it shows that the fast mechanical switch can move to the transient voltage insulation distance within 2 ms, and the simulation results are verified by electrical performance test. The successfully developed high-voltage and high-current fast mechanical switch has been put into practice in Zhangbei HVDC transmission test and demonstration project.