Terahertz (THz) radiation lies between the infrared and microwave range of the electromagnetic spectrum. Absorption spectrum in the THz range provides rich information about structure and weak interactions of biomolecules. THz absorption spectra of D-(-)-ribose, D-glucose, alpha-lactose monohydrate and beta-lactose were measured by terahertz time-domain spectroscopy (THz-TDS) in the frequency range of 0.3-1.6 THz at room temperature. The experimental results show that different saccharides have distinct THz absorption features, which suggests that THz-TDS is highly sensitive to molecular structures and components. Quantitative analysis of the mixtures of two to four saccharides was studied by linear regression with relative error less than 7.2%. The reasons for the relative error were discussed. The results demonstrate that THz-TDS is a promising and efficient method for both qualitative and quantitative analyses for pharmaceutical identification and biomolecular detection.