In November 2020,a dairy farm introduced a batch of dairy cows from other places.During the quarantine period,it was found that the dairy cows showed clinical symptoms such as elevated body temperature,depression,and loss of appetite.As the disease progressed,symptoms such as abdominal pain and diarrhea appeared Some sick cows died within about 24 hours after the onset,and the conjunctiva became cyanotic.Based on the clinical symptoms and pathological changes after anatomy of the affected cows,and through laboratory pathogen isolation and diagnosis,the author determined that the epidemic was caused by Pasteurella bovis.In order to provide reference for the subsequent diagnosis,prevention and control of similar epidemics,this article mainly introduces the diagnosis and treatment process of this epidemic.