Terahertz time-domain spectroscopy have been applied in research of four different varieties of Chinese green tea, the absorption and refractive Terahertz Spectrum of these tea were got in the range of 0.2 to 1.5 THz. Least Squares Support Vector Machines, Naive Bayes and Back Propagation Artificial Neural Network were applied to achieve Multi-class classification of these four kinds of tea, and the classification results of three algorithms were analyzed in detail. The results shows that support vector machine have better classification results in the experiment. This study demonstrated the feasibility of time-domain Terahertz Spectroscopy for the classification of difference kinds of tea.