Abstract: For developing further the application domain of oxidised cellulose, the 2,3-dialdehyde cellulose was prepared by selective oxidation of cotton fiber with sodium periodate, and the aggregated structure of the oxidized cotton fiber was analyzed by means of FT-IR and X-Ray,etc. The results showed that the crystallinity of cotton fiber increased after being slightly oxidised, but decreased after being severely oxidised. The breaking strength and elongation decreased as the degree of oxidation of cotton fiber increased.