Abstract: Wheat basal diet was control. The tested diets were wheat basal diet added with different levels of xylanase(0.05%, 0.10%, and 0.15% respectively). Each treatment was devised with 5 repeats and each repeat had 40 male Oreochromis niloticus. The fish in floating cages were fed to satiation for 75 days. The content of blood glucose in serum of 10 fishes from each treat was measured. The total RNA was extracted from the sample’s fore-gut and mid-gut with spin column total RNA extract kit. The SGLT1 expression was relatively quantified by means of RT-PCR. The results showed that, the xylanase could up-regulate SGLT1 expression of fore-gut, the amount of SGLT1 mRNA relative expression of 0.05%, 0.10% and 0.15% groups had increased by 19.28% (P<0.05), 42.17% (P<0.01) and 16.87% (P<0.05) over the control. As for the content of blood glucose, the control group was only 5.56mmol•L-1 when fed 2 hours later, the test groups which with xylanase supplement were influenced significantly at the same time. The blood glucose content of 0.10% group was higher significantly than that of the control (P<0.01). The weight gain rate of 0.05% and 0.10% groups were increased by 8.25% and 17.45% respectively (P<0.01), which were higher than that of the control, but it has no significant difference between 0.15% group and the control. So the conclusion is that adding appropriate amount xylanase to wheat basal diet can significantly up-regulate SGLT1 expression of fore-gut and serum glucose level, and promote the growth of Oreochromis niloticus. In this study we firstly investigated the influences of xylanase on Oreochromis niloticus’s SGLT1 expression. The quantification of SGLT1 carrier proteins expression would be further probed into in the future.