A THz time-domain spectrum analysis software is developed based on LabVIEW platform in order to deal with the issue that data processing software cannot be completely compatible with data acquisition software for present THz spectrographs. The algorithms for extracting optical information of samples in transmission and reflection THz spectroscopy, support vector machine (SVM) classification algorithms, and PLS algorithm are studied and programmed based on LabVIEW. All the source code of the software is LabVIEW language, with the functions of extracting optical information, classifying substance and analyzing concentration of multicomponent mixture. Moreover, the software is of high portability, extensibility, and compatibility with data acquisition software. The THz time domain spectrum of three kinds of plasticizers is analyzed with this software. The obtained refractive index and absorption coefficients show that three kinds of plasticizers can be distinguished by their THz spectrum and the software is reliable.