The invention provides a direct current circuit breaker used for controlling on-off of a high-voltage direct current power transmission system. The direct current circuit breaker comprises a control system, a protection branch, and a through-flow circuit and an LC forced transfer circuit which are in parallel connection, wherein the through-flow circuit consists of a circuit breaker body and an electric power diode which are connected in series; the LC forced transfer circuit consists of a first pre-charging capacitor, a first inductor and a thyristor which are connected in series; the response time of the thyristor is shorten than that of the circuit breaker body; the protection branch is used for performing voltage clamping when the voltages at the two ends of the through-flow circuit and/or the LC forced transfer circuit are greater than or equal to a voltage set value; the control system is used for controlling the on-off of the through-flow circuit and the LC forced transfer circuit; and the control system is used for transmitting a conduction signal to the thyristor before the circuit breaker body is disconnected so as to enable the current passing through the through-flow circuit to be lower than or equal to a first current set value at the disconnecting moment of the circuit breaker body.