The present invention relates to a pulsating current ripple cancelling circuit and a power converting system using the same cancelling circuit. The pulsating current ripple cancelling circuit includes a first transformer having a primary winding side and a secondary winding side; a second transformer having a primary winding side and a secondary winding side, wherein the primary winding side of the second transformer is electrically coupled with the primary winding side of the first transformer; a first diode electrically coupled with the secondary winding side of the first transformer; a first equivalent capacitor combination electrically coupled with the primary winding side of the first transformer; and a second equivalent capacitor combination electrically coupled with the secondary winding side of the second transformer.