The concept of time domain parameter is defined. In a small temperature region of (49±1)℃, dielectric spectroscopy of the time and frequency domains of a TGS single crystal is measured was FE phase transition of the crystal occurs. The results are devided into three components contributed by polarization of lattice, motion of electric domains, and activation of screen charges respectively. The latler two components make the ratio between static die-lectric constant and dielectric constant of acoustic frequency increase from 1 to 2.5 in this tem-perature region. The loss peak is provided mainly by screen charges, and the corresponding anomaly of free relaxation time appears near 48.615℃