The performance of 0.2 wt% Pd/SDB catalyst used for partial oxidation of ethylene to acetic acid has been evaluated in a fixed-bed reactor. The catalyst has high activity and selectivity toward acetic acid, but it starts to deactivate after running 84 h at 120degreesC and 1200 kPa. BET, XRD, FTIR and XPS have been employed to the characterization of the catalyst. It has been found that the deactivation of the catalyst is mainly due to the partial oxidative degradation of the SDB framework during reaction, particularly, in the presence of oxygen, which results in a decrease in surface area and an increase in hydrophilicity of the catalyst.