Abstract: The aim of the present study was to characterize the pathogenic bacteria associated with bovine endometritis in a dairy farm in Tongliao of Inner Mongolia. The uterine secretion samples were collected from dairy cows with endometritis to isolate pathogenic bacteria; the isolates were cultured and identified by the routine methods; the susceptibility of the strains against antimicrobial agents was assessed by disk diffusion method; the pathogenicity of the isolates to mice was preliminarily evaluated. The results showed that the characteristics of colony morphology in chromogenie medium and selective medium, gram staining, and biochemical reaction were in accord with those of Escherichia coli （E. coli）, therefore, the isolates were identified as E. coli; the pathogenic E. coli isolates associated with bovine endometritis showed high susceptibility to tluoroquinolones, aminoglycosides and cephalosporins but exhibited resistance to lincomycin and doxycycline; the death of mice challenged with E. coli isolates was observed, and the strains isolated from the tissue samples of dead mice were also identified as E. coli which were in accord with the clinical isolates, indicating that the E. coli isolates from bovine endometritis had pathogenicity to mice. The results obtained in this study provide scientific references for the effective prevention and treatment of dairy cow endometritis in this region.