Eight ancient bronze swords possessed at archaeological research laboratory of Hiroshima University were investigated non-destructively. Gamma-ray radiography using 137Cs and 60Co were developed to obtain transmission images of swords. X-ray fluorescence analysis were applied for the characteristic and qualitative elemental analysis of the swords. Magnetic response were also utilized to know the distribution of iron cores. It has been identified that all bronze swords has iron cores inside of the grip part of the sword. Up to now, existence of iron cores were assumed as a ritual symbol or functional meaning, but, it has revealed that these swords had originally iron blade, which were replaced to present bronze blade just to raise the commercial value. The connecting part was soldered and painted in bronze color. These findings are deeply related to the process of the production of bimetal swords in ancient Iran. Further researches on the ancient bimetal swords are needed.