Abstract: Dynamic changes of predominate bacteria in the uterus of postpartum dairy cows, and the relationship of uterus mucus characterestic and dominate bacteria community were investigated. Uterus mucus of total 42 dairy cows was collected on the 10, 20, 30 and 40 days after parturition, respectively. Bacteria were isolated and subsequently identified by aerobic and anaerobic cultures using standard bacteriological techniques. The results showed that the most prevalent bacteria in uterine after parturition were E. coli (85.7%), Proteus (64.3%) and Staphylococcus sp. (61.9%). The dominant bacteria on 10, 20, 30 and 40 days after parturition were Staphylococcus sp., Clostridium perfringens, Salmonella sp., Staphylococcus sp., respectively. It was found that E. coli had high isolation rate at each timepoint. The number of bacteria isolated from white or off white mucus and yellow or earthy yellow purulent mucus (5.6±0.4，5.5±1.4) were higher than that isolated from clear mucus (3.5±1.6). The isolation rate of Salmonella, Proteus sp., Streptococcus sp. and Arcanobacterium pyogenes from white or yellow purulent mucus were more than that from clear mucus on 30 and 40 days postpartum. Clostridium perfringens was associated with yellow or earthy yellow purulent mucus on 40 days postpartum. It indicates that the dominant bacterial community changes with time after parturition, and the characteristic of uterus mucus is associated with specific pathogenic bacteria.