Abstract: The species of pathogenic bacteria causing daily cow mastiffs varied in different geographic areas, and the incidences of mastiffs in different dairy farms also varied. In order to understand the epidemiology characteristics of bovine mastiffs in Bayannur area of Inner Mongolia, a total of 80 milk samples were collected from dairy cows with clinical mastiffs in four different dairy farms. A total of 51 bacterial strains were isolated and phenotypieally identified, including 31 Staphylococcus isolates,6 Streptococcus isolates, and 14 isolates of enteric bacilli. The results of this study was helpful for the understanding of species distribution of main pathogenic bacteria associated with dairy cow mastiffs in this region, and may provide scientific basis for the effective prevention and control of bovine mastitis and rational use of antimicrobial agents in veterinary clinic.