Abstract: Calves in a beef cattle farm in western Jiangxi Province were reported to have clinical symptoms of emaciation, loss of appetite and diarrhea. In order to identify the pathogenic agent associated with this disease, fresh fecal samples of calves with diarrhea were recovered, Bio-x five-line in situ rapid diagnosis kit of calf digestive tract was used for rapid diagnosis, isolation and identification of pathogenic bacteria were carried out, and in vitro susceptibility of the isolates against the commonly used antibiotics in veterinary clinic was tested. Rapid clinical diagnosis and laboratory diagnosis confirmed that the disease was caused by infection of Escherichia coli. The two isolates were highly sensitive to ciprofloxacin and completely resistant to penicillin, cefradine and other antibiotics. The diarrhea of calves in this cattle farm were well controlled using the antibiotic recommended by this study.