Microcrystalline cellulose(MCC) was activated with ultrasonic wave. The changes in supramolecular structure and morphology structure of MCC were studied by XRD and SEM. The influence of ultrasonic treatment on accessibility and oxidation reactivity of MCC with periodate sodium was investigated. The mechanism of the change of reactivity after ultrasonic treatment was discussed. The results showed that crystalline type of cellulose was not changed and no significant changes in crystalline size of cellulose were observed. However, after treatment with ultrasonic wave the crystallinity of cellulose decreased and morphology changes of the treated MCC was significant. These changes contributed to the increase of specific surface area and WRV, which implied the increase of accessibility. The reactivity of MCC with periodate sodium was successfully improved after ultrasonic treatment. The aldehyde content of its oxidized products dialdehyde cellulose(DAC) was improved from 71.3% to 85.0%. As the increase of ultrasonic treating time the aldehyde content first increased and then decreased.
