In this research, the chemistry of peroxide bleaching effect on rice straw pulp has been thoroughly studied both with lignin model compounds and with degradation of carbohydrates. Rice straw was cooked in by soda-(ethanol, diethylene glycol, dimethyl formamide) and kraft type. After three stage peroxide bleaching of organosolv pulps, some similarity in behavior of brightness and peroxide consumption for each alkali percentage has been observed. Final brightness of 63-70% ISO was attained for all tested pulps. The carbohydrates reaction in peroxide delignification results in a loss of viscosity due to attack by hydroxyl radicals to the carbohydrates chains. The yield loss in chemical pulping due to degradation and dissolution of polysaccharides (particularly hemicellulose) is substantial and constitutes a serious drawback of the process. The high obtained bleached yield for organosolv pulps (in the range of 90-91% o.d.p.) point to limited organosolv carbohydrate degradation during peroxide bleaching.