Poplar wood samples, cut into 0.8x0.8x4cm fragments, are subjected to dilute acid pretreatment at different conditions of time, temperature and sulfuric acid content (2-60 min, 120-190°C , 0-6.8% by weight). At the end of the reaction, the solid wood residues and the pretreatment water are recovered separately, then analyzed by HPLC, acid hydrolysis and Klason lignin to determine their chemical compositions in terms of sugar, lignin and inhibitor. Autoflurescence and colorimetry analyzes are also carried out on the solid samples.