Two hundred [(Duroc${ imes}$Yorkshire)${ imes}$Landrace] pigs were used in a 117-d growth assay (including four growth stages) to determine the effects of dietary supplementation of Lactobacillus reuteri on performance of swine, fecal and rectumal microflora and carcass grade. Pig diet was divided tow types, commercial diet (Control group) and supplemention of 0.1% Lactobacillus reuteri (Treatmental group). There was tend to increased in average daily gain (ADG) and feed efficiency (Feed/gain) in treatmental group than control group during the whole experimental period. The number of Lactobacilius spp. into rectum and feaces and carcass rate tended to increase in treatmental group than control group. Ammonia emission from excreta were decrease by supplemention of 0.1% Lactobacillus reuteri in feed (P<0.05). These results indicated that the dietary Lactobacillus reuteri were effective in performance, increasing of Lactobacilius spp. into rectum and feaces, decreasing ammonia emission from excreta, and it had also effective the carcass rate in swine.