The electromagnetic shielding and polarization characteristics of carbon fiber reinforce plastics (CFRP) based on unidirectional (UD) materials are determined by experiments. The UD CFRP laminates have single direction carbon fibers, which behave the same as wire-grid structures. The measured transmission coefficient for the 1 ply UD CFRP laminate is about -2dB, when the direction of the carbon fiber is perpendicular to the incident wave. The polarization ratio is more than 20dB for most frequency points. In addition, it is confirmed that the transmission coefficient can be controlled by rotating the UD CFRP laminates.