[Objective] To analyze the effect of probiotics on treating rumen acidosis of cows. [Method] 200 Chinese Holstein cows from a large-scale dairy farm in Shandong Province were selected as the experimental subjects.These cows were randomly divided into control group and experimental group with 10 replicates in each group and each replicate contains 10 cows.The control group was fed with a basic diet,and the experimental group was supplemented with 2.0% compound probiotics on the basis of basic diet.The significant differences in growth performance,lactation performance and rumen fermentation performance between two groups were compared and analyzed. [Result] The average daily weight gain of experimental group treated with probiotics was significantly increased compared to the control group（P<0.05）,and the feed to weight ratio was also significantly lower than that of the control group（P<0.05）.The average daily milk yield and milk fat percentage of experimental group were significantly higher than those of control group（P<0.05）.The pH value,acetic acid content,propionic acid content and butyric acid content of rumen fluid in the experimental group were significantly increased（P<0.05）。Lactic acid content and acetic acid/propionic acid ratio in experimental group were significantly lower than those in control group（P<0.05）. [Conclusion] The application of 2.0% compound probiotics could effectively relieve rumen acidosis of cows,which provided a reference for the efficient and scientific treatment of cow rumen acidosis in the future.