| The terahertz(THz)radiation occupies a large portion of the electromagnetic spectrum between 0.1THz and 10THz(1THz=1012Hz=300μm), its light sub- energy is only a few milli- Anne's electron volt. Compare with X-ray, it can be used to make non-destructive imaging. The interacting energy level among molecules, vibrational and rotational energy level of many big bio-molecules located in THz range, at this situation, THz time-domain spectroscopy becomes the complementarity of the infrared spectrum technology in many fields. THz-TDS is the phase coherent electromagnetic radiate detection technique in nature, which can directly measure amplitude and phase of the THz radiation pulse simultaneously. THz-TDS is the latest THz spectroscopy. In the spectrum measurement, the effect of noise on the measurement of interference is evident, If the noise intensity is too large, It can not easily identify the spectroscopy from the THz-TDS. Therefore, it really needs to reduce the noise form the system, which can extract useful signal to maximize.The THz-TDS has a high signal to noise (SNR), so we adopt the two classic methods of wavelet denosing: Spatially Correlation De-noising and the Threshold De-noising. Discuss the classic denosing principle and the mathematical basis, and on this basis, improve these two methods, then take the simulation validation. The Experiment results show that the new algorithms remedy the deficiencies of the traditional denoising method to some extent and the denosing effects have improved.Aim at the actual measurement of the water vapor absorption spectrum, this paper firstly adopts the two tradition wavelet denosing method, spatial correlation and the threshold methods to denoising the signal, and then adopts the improved methods. The simulation results show that the improved spatial correlation denoising can perfectly remove the noise from the sensor signal.
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