According to the recent study of the magnetohydrodynamic stability for both the global and local modes of field-reversed configurations (FRCs), it is required to develop a theory including the ion's finite orbit effect which is valid in FRCs. This means that the two dimensional analysis on the poloidal surface is inevitably necessary. As the first step toward the two dimensional stability analysis, the magnetic field coordinate is obtained numerically in FRCs for the first time. Using the co-ordinate, the equilibrium properties of FRCs are examined for the preparation of stability analysis.