Abstract: Milk samples of subclinical mastitis were collected from two dairy cow farms in Xinjiang, 91 strains of bacteria which contain 21 species were isolated and identificated from milk specimens. There were 28 strains of Staphylococci, 21 strains of Streptococcus, 25 strains of bacillus and 17 other strains, the rate was 30.78%, 23.07%, 27.48% and 18.67% respectively. Animal test of the main pathogenic bacteria had certained that the higher pathogenicity strains were Staphylococcus aureus, Klebsiella and E.coli. The results of 30 drugs sensitivity test showed pathogenic bacteria almost were ineffective to penicillin and tetracycline frequently used, while levofloxacin, furadantin, cefotaxim and amikacin had a fairly good bacteriostasis.

Key words: dairy cow subclinical mastitis; pathogenic bacteria; isolation and identification; pathogenicity; drug sensitivity test