The invention discloses a pre-charging circuit which comprises a first switch, a second switch, a diode, a first current limiting device, a capacitor and an inversion unit. One end of the pre-chargingcircuit is connected with a power grid, after the first current limiting device, the first switch and the diode are connected in series, one end of the series connected structure is connected with one end of the capacitor, and the other end is connected with a first-phase alternating current of the power grid. The other end of the capacitor is connected to a second-phase alternating current of the power grid sequentially through the inversion unit and the second switch, after the first switch and the second switch are closed, the current outputted by the power grid passes through a closed loop formed by the first current limiting device, the first switch, the diode, the capacitor, the inversion unit and the second switch to charge the capacitor. The circuit for pre-charging the bus capacitor is provided, is simple in, is changed rarely on the basis of an existing inverter system, and saves the cost.