Terahertz attenuated total reflection spectroscopy was employed to investigate the terahertz absorption spectra of different concentration glycine solutions within 20~450 cm^-1 at room temperature. There are four clear absorption peaks at 65.56, 127.28, 173.56, 308.55 cm^-1 respectively. The 2^nd derivative spectra and the multiple linear regressions were employed to perform the quantitative analysis of the glycine solution concentr-ation. Randomly combine different wave numbers, the optimum ternary linear regression equation was gained. The R² _Adj was 0.990 3, the Root Mean Square Error (RMSE) was 0.005 7, the Root Mean Squares Error of Prediction (RMSEP) was 1.658 9.