The microstructure and electromagnetic properties of melt-spun Nd-Fe-B nanocomposites, which have been dealt with by the ball milling process with different milling times, are studied specifically in this paper. The powder size ranges from 20 mu m to 5 mu m after different milling times. Moreover the powder particles even remain flake-like shape after 11 h milling time. X-ray diffraction spectra strongly suggest that all samples only have the single alpha-Fe phase. By using the complex permeability (mu = mu' - mu") and permittivity (epsilon = epsilon' -epsilon") within 2 to 18 GHz frequency range, determined by vector network analysis, the experiment shows that the permeability of flake-like Nd3Fe68Co18B11 can be increased while its permittivity is decreased by increasing the milling time. For the sample with 11 h milling time, its imaginary permeability mu" can be increased to an abnormal state below the frequency of 6 GHz. Based on transmission line theory, it is calculated that the Nd3Fe68Co18B11 composites can achieve their optimal reflection loss (RL = -8 dB) at 3.7 GHz with a matching thickness of 1.5 mm. This paper shows the possibility to obtain good microwave absorbing properties at a proper milling time for melt spun Nd-Fe-B nanocomposites. (C) 2011 Elsevier B.V. All rights reserved.