Terahertz (THz) time-domain spectroscopy technology is utilized to inspect the carbon fiber and glass fiber material and the field emission scanning electron microscope is assisted to observe sample morphologies. The study results show that, when the vibration direction of THz wave is perpendicular to the fiber sample direction, most signals can be acquired. The absorption coefficient slope of glass fiber is smaller than that of carbon fiber. Both the fiber diameter and fiber arrangement pattern have certain influences on the transmission capability of THz wave.