The present application discloses a power electronic transformer and a power supply system. The power electronic transformer is a single-phase power electronic transformer or a three-phase power electronic transformer, wherein each phase comprises: a plurality of power conversion modules; each power conversion module comprises a rectifier AC/DC circuit, a direct current (DC) bus capacitor, and a DC/DC circuit; an output terminal of the AC/DC circuit in each power conversion module is connected to an input terminal of the DC/DC circuit; the DC bus capacitor forms a parallel connection at the output terminal of the AC/DC circuit; input terminals of all the AC/DC circuits form series connections, and output terminals of all the DC/DC circuits form parallel connections together; each DC/DC circuit comprises n LLC resonance DC/DC units, input terminals of the n LLC resonance DC/DC units are connected in series and then connected to an output terminal of a corresponding AC/DC circuit, and output terminals of the n LLC resonance DC/DC units form parallel connections as output terminals of the DC/DC circuit; and n is an integer greater than or equal to 2. The power electronic transformer comprises a relatively small number of power conversion modules, thereby reducing the occupied space and the cost.