To expand the application of insulating glass fiber (GF) in the field of microwave absorption, one type of GF hybrids with carbon nanotubes (CNTs) and nickel (Ni) was successfully synthesized by chemical vapor deposition and electroless plating methods. By changing the reaction conditions, the morphology of GF hybrids including CNT's length, CNT's growth density, and Ni′s thickness could be adjusted. The as-produced hybrids were used as multifunctional reinforcement to fabricate epoxy composites. The dielectric properties of composites were particularly measured from 1 to 18 GHz. It was found that the variation of GF hybrids structure significantly changed the dielectric properties of the composites in the tested frequency range. Furthermore, the analytical simulation work based on the experimental results was conducted for optimizing the structural parameters of multilayered composites. The results showed that the best reflection loss of −60 dB with a −10 dB range of 5.6 GHz could be obtained in an absorber with a triple-layered structure composed by GF-CNTs/epoxy with different CNT contents and GF-CNTs@Ni/epoxy. Thus, the proposed hybrid method might be quite efficient for developing composites that can achieve high-performance electromagnetic absorbing