Cellulose is a polysaccharide compound having a crystal structure so difficult to dissolve in water. Degradation of cellulose to obtain useful substances (glucose, glyceraldehyde, and others ) can be done by acid hydrolysis, ionic liquid, enzymatic / fermentation, and hydrothermal processes. In this study the degradation of cellulose is done with a combination of sonication pretreatment and followed by hydrothermal processing in ionic liquids (NaCl and oxalic acid). Hydrothermal conditioin was conducted under CO2 and N2 gas at 200 bar. Temperature processing was 125 oC and 200 oC for various degradation time from 30 -180 minutes. After the degradation process the sample was separated as liquid and solid part, where the liquid is analyzed by the dinitrosalicylic acid method (DNS method) using a UV-Vis spectrometer to determine the reducing sugar. The solids were analyzed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) to understand the structure change. The results show that the glucose concentration increase with time of hidrothermal proessing and have a maximum at 120 minutes, and 90 minutes for 200 oC. The crystallinity and morphology of cellulose shown by XRD results and SEM. Product substances resulted in the degradation process was showed by LC-MS. Keywords: Polysaccharide, sonication, hydrothermal, ionic liquid, CO2, N2