Sugarcane straw is one of the most important residue from sugarcane processing. Its use is a very promising way to increase 2G bioethanol production. In this work, sugarcane straw was hydrothermally pretreated at different severity degrees (3.53-4.92). The experiments were performed at a Parr reactor at 180, 195, and 210°C (agitation speed of 200 rpm) for total reaction time of 40 min. Samples were withdrawn at 0, 5, 10, 15, 20, 30 and 40 min for chemical characterization of liquid fraction. It was found that the cellulose degradation and hemicellulose removal during the pretreatment step can be correlated with severity factor. The highest cellulose degradation (32.71%) and hemicellulose removal (84.98%) were reached for a severity factor of 4.68 and 4.30, respectively.