Abstract: The effects of xylanase on dough extensibility were studied using the Kieffer test of TA-XT Plus to determine the dough extensibility (Ex) and the resistance to stretching ( Rmax). The study showed that the Rmax of dough decreased and the Ex at Rmax increased with the dosage of xylanase increased. Xylanase softened and slacked the dough of wheat flour. At the same time, the effect of xylanase on different kinds of wheat dough rheology properties is different. the effect of different sources of xylanase on the same wheat dough rheology properties is different.