This study was investigated to observe Lactobacillus spp. population of poultry digestive organ, duodenum, ilium, cecum and colon by growing steps and to select of valuable lactobacilli as probiotics. Two strains of male broiler commercial chickens, Hybrid and Ross, were used to evaluate population of Lactobacillus spp. in intestinal tracts. Three strains of Lactobacillus were identified, and bile salts environment. The number of lactovacilli was the lowest in duodenum compared to other intestinal tracts which had similar population. Population of Lactobacillus was maintained constantly regardless growing steps after one week of age. Identification of Lactobacillus from cecum resulted in L.reuteri BC5, L. crispatus BC7, L.reuteri BC9. All strains was depressed in pH 1 and 2, although two strains could survive for one hour at pH 2. And they could survive at pH 4 for 4hours. In bile salts tolerance, L.reuteri BC5, L.crispatus BC7 were maintained for 2 hours, but the growth reduced from 2hours. Growth of L.reuteri BC9 was increased continuously. In conclusion, Lactobacillus of intestinal tracts were established at first week, and maintained constant population. They were influenced on severe acidic condition and bile salts. Cecal Lactobacillus has different growth charcteristics by strains.