Abstract: The magnetron sputtering was employed to sputter Al on the hollow glass microspheres. The electromagnetic characteristic of the composites consisting of Al-coated hollow glass microspheresFeCo powders was studied in the frequency range of 2~18GHz. The microwave absorbing property (R) of the composite was theoretically calculated. It has been found that the ε′,μ′and μ″  of the composites decreased with increasing the volume fraction of the Al-coated hollow glass microspheres, while ε″ has no significant change, when the overall volume fraction of Al-coated hollow glass microspheres and FeCo powders was fixed. The calculated peak value of R was moved to high frequency. The material with Al-coated hollow glass microspheres and FeCo powders volume ratio of 2∶1 and thickness of 2mm achieves the maximum absorbing value of -29.69dB, and the surface density is only 3.71kg/m2, and the bandwidth (with respect to -10dB absorption) is 2.4 GHz. Thus through changing the volume ratio of Al-coated hollow glass microspheres and FeCo powders, the electromagnetic parameter of the composite could be adjusted and the microwave absorbing property of the materials could be improved.