The terahertz wave frequency band is located between microwave and infrared. Because the electromagnetic wave in the terahertz band is at a lower energy level, it has better resolution on the intramolecular force (intramolecular hydrogen bond, etc.), molecular interaction and actions of organic molecules like vibration and rotation. Carbohydrates are typical organic molecules, in which glucose (C6H12O6) has many isomers whose uses are differently. In this paper, the terahertz time-domain spectroscopy technique is utilized to measure four kinds of isomers of sugars in the range of 0.1-2.0 THz, and the absorption spectrums of the measured substance in solid state are obtained under ideal thickness. The differences in the spectrums are explained from the perspective of molecular space structure and intramolecular hydrogen bonding; the phenomenon is predicted that the absorption intensity and the absorption frequency point position of each solution may change with the concentration of the solution. The correctness of the prediction is confirmed by the obtained absorption spectra. It is also discovered that the absorption spectra of solid saccharide and its aqueous solution are strongly correlated.