Abstract:  This experiment was conducted to investigate the effects of Bacillus thuringiensis BtZ01 on the growth performance，intestinal development and microflora of post-embryonic mice. A total of 48 pregnant mice were randomly allocated to 4 groups: control group fed with sterilized water and other three treatment groups fed with sterilized water containing 106， 108， 5×109 cfu·mL-1 BtZ01， respectively. Trial lasted 66 days which from mice pregnant to the post-embryonic mice grown-up. The results showed as follows：1） Drinking water added with Bacillus thuringiensis BtZ01 had no significant effect on weight， length and feed/gain of post\|embryonic mice （P>0.05）. 2） The relative weight of jejunum-ileum and colon-rectum of post\|embryonic mice at weaning （P<0.05） was significantly decreased in the treatment of 5×109 cfu·mL-1 Bacillus thuringiensis BtZ01. Adding Bacillus thuringiensis BtZ01 of 106 and 108 cfu·mL-1 levels had no significant effect on relative weight and correction length of small intestine of post\|embryonic mice at weaning and adulthood （P>0.05）. 3） The villous length and V/C value of jejunum of post\|embryonic mice at adulthood （P<0.05） was significantly increased in the treatment of  108 and 5×109 cfu·mL-1 Bacillus thuringiensis BtZ01. 4） The number of E.coli in caecum of post\|embryonic mice （P<0.01） was extremely significantly decreased in the treatment of 108 and 5×109 cfu·mL-1 Bacillus thuringiensis BtZ01. In conclusion， high dose of Bacillus thuringiensis BtZ01 has certain inhibitory effect on intestinal development of post-embryonic mice in youth. But over the long\|term feeding result， drinking water added with Bacillus thuringiensis BtZ01 could improve intestinal villi development and the function of digestion and absorption and have an ability to inhibit the harmful bacteria to colonization.

Key words: Bacillus thuringiensis, post\, embryonic mice, intestinal development, microflora