E. coli, Enterococcus, Staphlococcus, Lactobacillus, Bacteriodes, Bifidobacterium and Pullorum in rectum Of the seven-day-old chickens in different physiological conditions were studied quantitatively. A statistical analysis revealed the quantitative change between S. pullorum and six predominant instestinal bacterial floras and the mieroecological pathogenetic mechanism of pullorosis of chicken. Besides, the ecological therapy of chicken pullorosis was also discussed.