Abstract: Three different desalting modes of xylan extractives by ultrafiltration were examined, which include continuous desalting followed by concentration (mode A), the opposite (mode B) and batch desalting (mode C). It was shown that the inorganic salts and the substances with low molecular weight in xylan extractives could reduce the solvent flux during ultrafiltration. When xylan extractives were desalted by ultrafiltration, the optimum number of diavolume was 4. At this time, the total removal ratios of Na + by mode A, mode B and mode C were 93%, 92% and 96% respectively. Mode B consumed half as much water as others did, saved about 30% of the total operating time required by others, and gave a total reducing sugar recovery of 97%. So mode B was thought as the optimum mode economically. But if the higher removal ratio was necessary, mode C should be used. At the number of diavolume of 4, the removal ratio was 96% and the total reducing sugar recovery was 97% with mode C.