Using linear low-density Polyethylene (LLDPE)/ethylene-octene copolymer (POE) as a polymer matrix and carbonyl iron powders (CIPs) as filler, we prepared polymer matrix composites with microwave-absorbing properties by means of melt blending. Scanning electron microscopy and transmission electron microscopy were used to characterize the samples. The absorbing properties of the composites were measured with the arch method in the range of frequency, 2.0-18.0 GHz. The results indicate that the absorbing peaks moved to low frequency as the CIP content in composites increased and that there was an appropriate CIP content in LLDPE/POE/CIP composites to achieve the best absorbing effectiveness. The electromagnetic parameters of the composites were determined with the transmission/reflection method in the range 2.6-17.8 GHz. The experimental results show that there were both dielectric loss and magnetic loss ill the LLDPE/POE/CIP composites. Therefore, the microwave absorption of the LLDPE/POE/CIP composites was attributed to the combining, contribution, of the dielectric loss and magnetic loss. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1911-1916, 2009