The changes of circular permeability with the circular magnetic field and frequency, in amorphous and nanocrystalline soft magnetic wires with different magnetic strucutre, have been determined from the measurements of impedance. The circular magnetization curve was obtained by using the Chen et als formulas. We found that these formulas are not suitable for the process with very large magnetic losses, so a general expression has been developed. Additionally, different circular coercivity mechanisms in the wires with longitudinal or transversal domain strucutre were deduced from analyzing the circular-field-dependent complex circular permeability. Finally, the frequency effect is also discussed.