The invention provides a multi-stage voltage-stabilized main circuit device for simulating photovoltaic assembly characteristics of a power supply. The device mainly comprises a plurality of circuits; the main part includes a main power circuit and a control circuit; the main power part comprises a rectifying filtering circuit, a switching voltage-stabilized power supply and a linear voltage-stabilized power circuit; a switching tube of the switching power supply can be adjusted to be cut off and closed to adjust the outputted voltage current; the linear power circuit is used for further stabilizing the voltage to reduce ripple and noise; the main part is that the output voltage and the output current of the switching voltage-stabilized power supply and the linear voltage-stabilized power supply are detected to determine a curve working point, the reference voltage is generated to control the cut-off and closing time of the switching tube so as to change the output of the multi-stage voltage-stabilized main circuit device; with the adoption of the method, the output of the power supply can be automatically adjusted according to the change on load, and moreover, the solar characteristics curve can be accurately simulated.