Biomass extracts, particularly sugars and other useful derivatives, from biomass hydrolysis are important products for further conversion to the production of biofuels. This paper investigates the hydrolysis of cellulose as a model compound of biomass in hot-compressed water using a continuous flow system. A series of experiments were carried out to investigate the effects of reaction conditions (e.g. temperature, pressure, water flow rate, etc.) on cellulose conversion and the concentration of the extracts. The residues remaining in the reactor after partially hydrolysis reactions were collected, dried and characterised by SEM and XRD. The liquid samples from the filtered stream were analysed for carbon concentration using TOC analyser and sugar concentration using HPLC. The results show that cellulose in the reactor can be completely hydrolysed with 10 min flow of hot compressed water at 280 ºC and 20 MPa. The rate of hydrolysis increases significantly with reaction temperature but pressure appeared to have insignificant effect on the rate of cellulose conversion. The rate of hydrolysis is also insensitive to the water flow rate while the depolymerization of the hyrolysis products is suppressed as the water flow rate increases. The liquid samples were clear but white substance precipitates from the liquid samples after sufficient long time (at a scale of hours). Analysis of the precipitates after 24 h settling at room temperature indicate that the precipitates mainly consist of the polysaccharides and their amount increase with reaction temperature, while the main products in the liquid samples are oligo- and monosaccharides.