The field of terahertz (THz) science and technology has achieved significant progress over the last decades. Research interest focuses on THz spectroscopy and imaging. The signal-to-noise ratio (SNR) of the THz system is of great importance in the application of THz spectroscopy and imaging. In this letter, the wavelet de-noising technology is used to improve SNR and increase the speed of the THz time-domain spectroscopy system by reducing the repeating times.