The trial was conducted to study the effects of different levels of xylanase on the nutrients utilization, digestive-related organs development of broilers fed wheat-based diets. Two hundred and forty 1-day-old Arbor Acres broilers were allocated to 4 dietary treatments （with 5 replicates of 12 chicks each） in a randomized complete block design. A wheat-corn-based basal diet containing 40% wheat was designed with 0, 500, 1 000 and 5 000 U/kg xylanase supplemented, respectively. The trial lasted for 21 d. The results showed that supplementing xylanase improved the apparent dry matter digestibility (P=0.093) and AME (P=0.110), but the apparent utilization ratio of crude protein, Ca and P and fecal moisture ratio was not significantly improved in broilers at 17～21 d (P>0.05). No significant differences were observed in the nutrients utilization among the xylanase groups (P>0.05). Supplementation of 1 000 U/kg xylanase decreased significantly the relative length of ileum of broilers at 21 days of age (P<0.05). No significant differences were observed in the relative weight of intestine, gaster, pancreas and spleen of broilers at 21 days of age among groups (P>0.05). Supplementation of xylanase did not affect significantly tibia weight and length, ash and P content in tibia of the broilers at 21 days of age. These data indicated that xylanase, even over supplementation did not significantly improve nutrients utilization and most of digestive-related organs development of broilers fed diets with 40% wheat, and increasing supplementation of xylanase had no deleterious effects.［Chinese Journal of Animal Nutrition, 2010，22（1）:157-162］