A resonant converter, comprising: an input power supply, a bleeder circuit comprising a capacitor C1 and a capacitor C2 that are connected in series, a multi-level switching network, a resonant unit, and a transformer, wherein a positive electrode and a negative electrode of the input power supply are respectively connected to two ends of the bleeder circuit, and the bleeder circuit is configured to divide a direct current voltage that is input by the input power supply; two input terminals of the multi-level switching network are respectively connected to the two ends of the bleeder circuit, a clamping middle point of the multi-level switching network is connected to a middle point of the bleeder circuit, and a quantity of output levels at an output terminal of the multi-level switching network is greater than 3; one end of the resonant unit is connected to an output terminal of the multi-level switching network, and another end of the resonant unit is connected to one end of a primary side of the transformer; the other end of the primary side of the transformer is connected to the middle point of the bleeder circuit; the multi-level switching network is configured to work in different working modes or in different working manners of one working mode according to control instructions of a control apparatus (7, 50), wherein the control instruction is given by the control apparatus based on a working parameter of the resonant converter, and the control apparatus is located in a power conversion system comprising the resonant converter; and the output terminal of the multi-level switching network is configured to output square wave voltages with different amplitudes in the different working modes or in the different working manners of one working mode, to serve as input voltages of the resonant unit, wherein the input voltage is used to adjust a gain of the resonant converter. an input power supply, a bleeder circuit comprising a capacitor C1 and a capacitor C2 that are connected in series, a multi-level switching network, a resonant unit, and a transformer, wherein a positive electrode and a negative electrode of the input power supply are respectively connected to two ends of the bleeder circuit, and the bleeder circuit is configured to divide a direct current voltage that is input by the input power supply; two input terminals of the multi-level switching network are respectively connected to the two ends of the bleeder circuit, a clamping middle point of the multi-level switching network is connected to a middle point of the bleeder circuit, and a quantity of output levels at an output terminal of the multi-level switching network is greater than 3; one end of the resonant unit is connected to an output terminal of the multi-level switching network, and another end of the resonant unit is connected to one end of a primary side of the transformer; the other end of the primary side of the transformer is connected to the middle point of the bleeder circuit; the multi-level switching network is configured to work in different working modes or in different working manners of one working mode according to control instructions of a control apparatus (7, 50), wherein the control instruction is given by the control apparatus based on a working parameter of the resonant converter, and the control apparatus is located in a power conversion system comprising the resonant converter; and the output terminal of the multi-level switching network is configured to output square wave voltages with different amplitudes in the different working modes or in the different working manners of one working mode, to serve as input voltages of the resonant unit, wherein the input voltage is used to adjust a gain of the resonant converter.