<p>In this research, hydrothermal treatment of glucose was conducted at temperatures ranged from 140 °C to 220 °C, with reaction times between 2.5 min and 20 min. Liquid products obtained after the hydrothermal process were quantitatively analyzed by the mass spectroscopic method and high performance liquid chromatography (HPLC) analyzer. The in situ MS analysis revealed that decomposition rate of glucose was enhanced at the higher temperature. The results showed that the presence of 5-hydroxymethylfurfural (5-HMF) and other low-molecular-weight of acids, whose concentration increased when the temperature increased to 180 and 220 °C. The reaction pathway of glucose decomposition was purposed follow products obtained by in situ MS analysis and HPLC and the kinetic parameters for the pathway of glucose under hydrothermal conditions have been achieved by assuming first-order reactions.</p>