The invention relates to the field of high voltage DC circuit breaker, in particular to a high voltage DC circuit breaker. The fast mechanical switch of the high voltage DC circuit breaker is arrangedoutside the circuit breaker valve tower, and only the electrical distance between the fast switch and the rest parts needs to be considered. During the opening and closing process, the vibration of the fast mechanical switch does not affect the circuit breaker valve tower and the electromagnetic compatibility performance is excellent. Meanwhile, the fast mechanical switch is arranged on the ground so as to facilitate equipment operation and maintenance. The fast mechanical switch of the medium-high voltage DC circuit breaker adopts the SF6 fast switch so as to improve the arc extinguishing capability and breaking capacity of the switch. For higher voltage grades, SF6 arc extinguishing medium is adopted so as to reduce the number of breakers of the circuit breaker, avoid the situation of inconsistent switching characteristics among multiple breakers of the circuit breaker and improve the reliability of the circuit breaker, and SF6 has faster response speed.