There is good application prospect in the transmission and grid-connection of large-scale wind power and other renewable energy of VSC-HVDC transmission grid with overhead lines. Due to the rapid rise of DC current under DC line fault, DC circuit breaker with high speed and large capacity is generally used to isolate DC faults in the VSC-HVDC engineering. However, the manufacture of DC circuit breaker is difficult and costly, which hinders the development of DC grid. Then, VSC-HVDC transmission grid based on hybrid MMC and fast vacuum breaker is proposed. It makes full use of the control ability of hybrid MMC, it can ensure that the converter does not lock during the DC fault, so that the DC power grid can quickly and flexibly switch to a new operation state after the DC fault is cleared. The power interruption time of the DC grid is shortened, which can improve the utilization of the DC grid. At the same time, the fast vacuum breakers are installed in the DC line to replace the high-speed large-capacity DC circuit breaker, so as to reduce the construction cost of the DC grid. Finally, simulations based on PSCAD/EMTDC platform are executed to verify the correctness of this method.