In recent years, Electromagnetic wave (EMW) absorption materials have received great interests owing to their ability of addressing the increased EM radiation (EMR) and interference (EMI) problems. With the advantages of high magnification saturation and large permeability in GHz range, cobalt materials have been considered as promising EM absorbers. This article introduces the development of pure Co materials with different micro-structures and Co/C composites as EM wave absorption materials. The effects of various microstructures, filling ratios, and graphitization degree on the EM wave absorption properties were thoroughly discussed. Through comparisons of different types of Co based absorbers, the combination of Co and porous carbon can be an effective method and main direction to reach the requirements of ideal EMW absorption materials with strong absorption, low thickness, broad absorption bandwidth and low density.