This paper deals with the use of Liquid-phase thermogravimetry to investigate the reaction kinetics of cellulose in hot compressed liquid water. The liquid-phase thermogravimetric measuring system employed in this study is equipped with a magnetic suspension balance that can measure the weighing force without contact. Thus, a high pressure and temperature reactor is used, with the main body of the balance located outside the reactor. Using this system, the cellulose weight decay was observed under isothermal and nonisothermal conditions over a temperature range up to 300 degrees C at 10 MPa. The weight decay rate obtained obeyed first-order kinetics, with its activation energy around 220 kJ/mol. The kinetic constants obtained in this study were found to be reasonable when compared to previously reported parameters.