A pilot-scale apparatus for continuous supercritical and near-critical water reaction was set up. A high-pressure slurry supplying system was developed to feed the solid material-water slurries. The apparatus features temperature up to 600 degreesC, pressure up to 40 MPa, residence time from 24 s to 15 min, maximum amount of slurry supply of 2.4 L.h(-1), maximum solid content of slurry up to 10% (by mass) for cellulose from Merck, and resistance to corrosion. Long-time runs of decomposition of cellulose were carried out and steady runs were confirmed. Kinetics of cellulose decomposition was studied. The apparent activation energy evaluated was 147 kJ.mol(-1). In addition, a new three-step pathway for cellulose hydrolysis was proposed. The derived kinetic equation is in good agreement with the experimental data.