A discharging method of a bus capacitor, applied to a bi-directional DC-DC converter, wherein the bidirectional DC-DC converter comprises a first bus capacitor, a second bus capacitor, a first switch and a second switch connected in series, and a third switch and a fourth switch connected in series, two series connection points are respectively connected to two terminals of a reactor, wherein the first switch, the second switch, the third switch and the fourth switch are each provided with an anti-parallel diode; an emitter of the first switch is connected to a collector of the second switch, and a connection point is connected to a terminal of the reactor; an emitter of the third switch is connected to a collector of the fourth switch, and a connection point is connected to the other terminal of the reactor; a collector of the first switch is connected to a terminal of the first bus capacitor; an emitter of the second switch is connected to the other terminal of the first bus capacitor; a collector of the third switch is connected to a terminal of the second bus capacitor; an emitter of the fourth switch is connected to the other terminal of the second bus capacitor; and the discharging method of the bus capacitor comprises: detecting a voltage across the first bus capacitor and/or a voltage across the second bus capacitor; determining whether the voltage across the first bus capacitor and/or the voltage across the second bus capacitor meets a preset condition, after the DC-DC converter or the inverter is powered off, wherein the preset condition indicates that the first bus capacitor and/or the second bus capacitor requires discharging; controlling, in a case that a voltage across the first bus capacitor meets the preset condition, the fourth switch to be turned on, until the voltage across the first bus capacitor does not meet the preset condition; and controlling, in a case that a voltage across the second bus capacitor meets the preset condition, the second switch to be turned on, until the voltage across the second bus capacitor does not meet the preset condition; and is characterized by comprising: controlling, in a case that a voltage across the first bus capacitor meets the preset condition, the first switch to be turned on in response to a first preset periodic pulse, until the voltage across the first bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the first switch in each period of the first preset periodic pulse; and controlling, in a case that a voltage across the second bus capacitor meets the preset condition, the third switch to be turned on in response to the first preset periodic pulse, until the voltage across the second bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the third switch in each period of the first preset periodic pulse. detecting a voltage across the first bus capacitor and/or a voltage across the second bus capacitor; determining whether the voltage across the first bus capacitor and/or the voltage across the second bus capacitor meets a preset condition, after the DC-DC converter or the inverter is powered off, wherein the preset condition indicates that the first bus capacitor and/or the second bus capacitor requires discharging; controlling, in a case that a voltage across the first bus capacitor meets the preset condition, the fourth switch to be turned on, until the voltage across the first bus capacitor does not meet the preset condition; and controlling, in a case that a voltage across the second bus capacitor meets the preset condition, the second switch to be turned on, until the voltage across the second bus capacitor does not meet the preset condition; and is characterized by comprising: controlling, in a case that a voltage across the first bus capacitor meets the preset condition, the first switch to be turned on in response to a first preset periodic pulse, until the voltage across the first bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the first switch in each period of the first preset periodic pulse; and controlling, in a case that a voltage across the second bus capacitor meets the preset condition, the third switch to be turned on in response to the first preset periodic pulse, until the voltage across the second bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the third switch in each period of the first preset periodic pulse. controlling, in a case that a voltage across the first bus capacitor meets the preset condition, the first switch to be turned on in response to a first preset periodic pulse, until the voltage across the first bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the first switch in each period of the first preset periodic pulse; and controlling, in a case that a voltage across the second bus capacitor meets the preset condition, the third switch to be turned on in response to the first preset periodic pulse, until the voltage across the second bus capacitor does not meet the preset condition, wherein a current of the reactor decays to zero in a turn-off time of the third switch in each period of the first preset periodic pulse.