Objective To study the gene homology of intestinal colonized and infectious bacteria in ICU patients to provide the epidemiological and molecular biological basis for formulating the control measures of multi resistant bacterial hospital infection. Methods The multi-drug resistant colonized bacteria isolated from the anal swabs and the same multi-drug resistant bacteria isola-ted from the clinical samples in the same patients were matched.The Diversilab automatic repetitive extragenic palindromic(REP)-PCR typing system was adopted to analyze the gene homology of multi-drug resistant colonized bacteria and infectious bacteria in the intestinal tract.Results 4 pairs of multi-drug resistant colonized bacteria and the same multi-drug resistant bacteria isolated from the clinical samples on admission in the same patients were selected and performed the homology detection,2 pairs had the ho-mology and 2 pairs had no homology;4 pairs of multi-drug resistant colonized bacteria and the same multi-drug resistant bacteria isolated from the clinical samples in the patients with hospital infection were performed the homology detection,4 pairs all showed the homology.Conclusion The multi-drug resistant colonized bacteria and the infectious bacteria in ICU patients have the homolo-gy.The multi-drug resistant colonized bacteria can cause the occurrence of hospital infection,so their management should be strengthened in clinic.