Abstract: In order to detect and investigate the morbidity of mastitis of lactating cows in a dairy farm in Korla City of Xinjiang, the subclinical mastitis of 32 lactating cows in this dairy farm was detected. The results showed that the positive rate of bovine subclinical mastitis was 40.63%, and the positive rate of mastitis increased with the increasing of the reproductive cycles of the cow. The positive rate of mastitis in dairy cows with milking machine was higher than that with manual milking. And the positive rate of mastitis at back mammary gland was higher than that at front mammary gland.