Reduce the consumption of chlorine dioxide in the bleaching of pulp is one of the main problems of technology of production of bleached pulp at Russian enterprises. We have developed a modified method of bleaching of sulphate hardwood pulp with a degree of ozonization. The new in work is the identification of the mechanism of ozonation on the structure of cellulose at different stages of the pulp bleaching. To assess structural changes of cellulose in the process of bleaching was used technique for IR spectroscopy. To characterize the hydrophilic properties of the cellulose used a calorimetric method and the method equilibrium sorption.Shown an advantage of using both chlorine dioxide and ozone in the bleaching of sulphate hardwood pulp. The obtained results of physical and chemical research associated with physico-mechanical properties of bleached and unbleached cellulose at different stages of bleaching. Shows the effect of ozonation on the mechanism of interaction of cellulose with bleaching agents. Effective delignification in the joint use of ozone and chlorine dioxide, can reduce the cost of bleaching chemicals. The brightness level corresponds to the world standards. and the content of organochlorine compounds (AOH) decreased by 30%. Reduce the consumption of chlorine dioxide helps to reduce contamination of waste water, reducing the content of organochlorine compounds (AOH).