Abstract: The configurations of an interleaved flyback converter and a controlling method thereof are provided. The proposed two-phase interleaved flyback converter includes a transformer including a first primary winding having a first terminal, a first secondary winding having a first terminal, a second primary winding having a second terminal, a second secondary winding having a second terminal and a magnetic coupled core device, wherein the first primary, the first secondary, the second primary and the second secondary windings are wound therein, and the first terminal of the first primary winding has a polarity the same as that of any of the first terminal of the first secondary winding, the second terminal of the second primary winding and the second terminal of the second secondary winding so as to eliminate a ripple of a channel current of the converter.