Abstract: Objective Investigate and research for pathogenic bacteria causing diarrhea and hemolytic uraemic syndrome (HUS) in Henan Province from 17 March to 6 Huly 2000.Methods 620 samples collected from patients,domestic animals and poultry were tested with Mec broth enrichment,immunomagnetic separation IMS , CHROMagarO157 medium isolation and rfbO157 and rfbO111 primers muti - PCR.Results 99 E.coli O157:H7 strains are isolated.56 of them were positive for rfbO157.Shiga toxin type 2(stx2)、enterohemolysin (encoded by CHEC hlyA)、intimin (encoded by eaeA) and Verocytotoxins virulence test. 7 stains can produce less virulence factors.36 of them were neg-ative for virulence factors. Conclusions The tests showed that 99 e.coli O157:H7 strains had various colon shapes and colors on CHROMagar - O157 medium,and different biochemical reaction as well as viruience factors. This study is helpful for determination on bacteria,control of contamination resources and research at bacterial toxicology.