Abstract: The study was conducted to examine the effects of wheat based diet supplemented with two xylanase preparations(native xylanase EⅠ, foreign commercial xylanase EⅡ) on the mean retention time(MRT) of digesta and nutrient digestibility in segments of gastrointestinal tract of broiler chickens．Seven-day-old broiler chickens were divided into five groups，wheat based diets was supplemented with EⅠ(A1 Group), 0.02% EⅠ(A2 Group), 0.02% EⅡ(B1 Group), 0.05% EⅡ(B2 Group), 0%(C Group) for 14 days respectively．The results showed that the MRT in jejunum and ileum were the longest in all groups．The MRT in proventriculus, colon and ceca were prolonged by xylanase supplementation，and in other segments of intestinal tract the MRT were shortened，but no significant effects were observed. A1, A2, B1 and B2 groups reduced total MRT by 15.2%, 6.4%, 13.6% and13.8%, respectively. Groups with xylanase increased dry matter and crude protein digestibility in feces. In all groups，digestibility of dry matter and crude protein was negative in crop, proventriculus, duodenum and ceca， while that in gizzard, jejunum, ileum and colon was positive．There was a tendency of increase from jejunum to colon.