The present invention relates to an Fe-modified perovskite-type catalyst, a method for preparing same and a method for preparing a synthesis gas by a combined reforming reaction using same. More particularly, it relates to a catalyst for a combined natural gas/steam/carbon dioxide reforming reaction having a perovskite structure with La and Sr introduced at the A site and Ni and Fe introduced at the B site with specific molar ratios and a method for producing a synthesis gas for Fischer-Tropsch synthesis or methanol synthesis using the catalyst by the combined reforming reaction. The catalyst of the present invention exhibits higher carbon dioxide conversion rate, significantly reduced catalyst deactivation caused by carbon deposition and improved long-term catalyst stability and activity, as compared to the existing catalyst for reforming reaction prepared by the impregnation method.