This article deals with an analysis of the components of crucible steel, which was made in Iran. It is very important so one can learn about the internal structure of this precious steel. Because all physical attributes of this type of steel such as sharpness, flexibility, sturdiness, white lines set in blackish/grayish background are all due to the elemental components of this type of steel and as well due to the processes of making crucible steel, forging, quenching, and tempering. To understand the components and the internal structure of the crucible steel some samples were taken from four antique Persian swords kept in the Cultural Institute of Bonyad.