Abstract: A total of 360 newly-hatched AA broilers were randomly allotted into five dietary treatments with 6 replications of 12 broilers. The five experimential diets were consisted of corn-soybean meal basal diet without antibiotics as control treatment and the other four ones which supplemented the basal diet with 0.3% FOS, 0.1% Bacillus subtilis, 0.3% FOS + 0.1% Bacillus subtilis, and 22.5 mg/kg Aureomycin, respectively. The result indicated that dietary supplementation with FOS or Bacillus alone had selective effects on increasing caecal population of Lactobacillus and decreasing population of E. Coli and Salmonella. However, supplemental Aureomycin had non.selective effects on caecal microflora which inhibited all bacteria. Moreover, the combination of FOS and Bacillus had much better improvement on caecal micro.ecosystem for broiler cockerels. Fecal emission of ammonia and sulfureted hydrogen decreased by 38.38% (P<0.05) and 24.35% (P<0.05) resulted from addition of FOS and by 62.14% (P<0.05) and 28.49% (P<0.05) for combination of supplemental FOS and Bacillus, whereas no effect was significant (P>0.05) due to dietary supplementation with Bacillus or Aureomycin. Availability of crude ash increased by 18.94% (P<0.05), 17.36% (P<0.05) and 23.66% (P<0.05), calcium by 20.78% (P<0.05), 14.63% (P<0.05) and 21.31% (P<0.05), and Phosphorus by 6.60%(P>0.05), 12.32% (P<0.05) and 14.67% (P<0.05), respectively, resulted from dietary supplementation with FOS, Bacillus and combination of FOS and Bacillus.