Based on Maxwell equations, the theoretical formulas of microwave electromagnetic parameters of polycrystalline iron fiber absorber are dervied. The anisotropy of microwave electromagnetic parameters of polycrystalline iron fiber absorber is explained by use of numerical calculations. Some samples of fiber orientation have been produced and their electromagnetic parameters have been tested, the results confirm the anisotropy of electromagnetic parameters. Both of the theoretical and experimental results demonstrate that the axial permeability of polycrystalline iron fiber is greater than its radial permeability, and the axial permittivity of polycrystalline iron filber is greater than its radial permittivity.