A terahertz time-domain spectrometer is employed to study various properties of jade, including the
kind identification and polarization analysis. The characteristic absorption spectra and refractive index
of jade are obtained in the range of 0.2 to 2.6 THz. Studying the absorption spectra and the
transmission temporal THz waveform with two peaks, which were confirmed to be coming from
ordinary and extraordinary beams, respectively, and result in fake absorption features. A practical ways
are suggested to remove the fake absorption features and therefore the real absorption spectra of jade
which accurately indicate the information of the samples can be obtained.