Summary form only given. Nanocrystalline structure in Fe- and Co-based soft magnetic materials is a key factor in showing low magnetic loss and high permeability at frequencies ranging to GHz. Previous studies on such materials explain the contribution of nano-sized crystal precipitates existing in amorphous matrix to high frequency magnetic property improvement. The improved properties are achieved in the form of small-sized magnetic domain structure by (1) the reduction of apparent magnetic anisotropy due to the accommodation of each nano-sized grain's local anisotropy, (2) the creation of small magnetostrictive crystalline phases and (3) the increase of electrical resistivity in the presence of the phases. The next step investigation of nanocrystalline magnetic materials has to be focussed on determining which contribution of the three terms is emphasized in evaluating magnetic properties affected by microstructural control. This paper presents the relationship between magnetic properties and microstructural evolution of annealing-processed Fe-Zr-B-Ag film deposited on Si substrate which is known to possess the high saturation magnetization and high permeability.