[Objective] To study the effects of probiotic fermented feed on the intestinal flora and production performance-related indexes of dairy cows. [Method] Adopted a single factor randomized trial design,200 Holstein cows with similar age,parity and average milk yield were divided into four groups：control group（basic diet）,low-dose group（basic diet+1% probiotics）,medium-dose group（basic diet+2% probiotics）and high-dose group（basic diet+4% probiotics）. Each group was configured with five replicates.The number of cows in each replicate was the same.The pre-test lasted for 7 d,and the formal test lasted for 35 d.The average daily weight gain,average daily milk yield and feed to milk ratio of dairy cows were statistically analyzed during the formal test,and the quantities of Escherichia coli,Salmonella and Lactobacillus in the feces on day 35 were detected. [Result] Compared with the control group,the average daily feed intake and average daily milk yield of low-dose,medium-dose and high-dose groups increased significantly;the ratio of feed to milk in the low-dose,medium-dose and high-dose groups was significantly reduced; the quantities of Escherichia coli and Salmonella in feces of low-dose,medium-dose and high-dose groups decreased significantly;the quantities of Lactobacillus in feces of low-dose,medium-dose and high-dose groups increased significantly.In addition, in the high-dose group,the average daily feed intake,average daily milk yield and Lactobacillus quantity in feces were the highest,and the ratio of feed to milk and the quantities of Escherichia coli and Salmonella in feces were the lowest. [Conclusion] The probiotic fermented feed can effectively improve the growth performance and intestinal flora of dairy cows,and the optimal dosage is 4%.