Abstract: In order to analyze the nutrient composition of Holstein milk and Jersey milk under high-altitude feeding and its correlation with bacterial diversity, the nutrient components and bacterial diversity of the two types of milk were determined and correlation analysis was carried out in this study. The results showed that there were significant differences in the contents of basic components (fat, protein, dry matter and non-fat solids) and 14 amino acids, as well as in mineral contents of calcium and phosphorus, in the two types of milk (P<0.05). Their bacterial communities were similar in structure but different in abundance, with Cetobacterium, Aeromonas, Bacteroides, Akkermansia, Pseudomonas and Lactobacillus being their common dominant genera. Heatmap of Spearman correlation analysis showed a correlation between bacterial community and milk composition. To sum up, the quality of Jersey milk was better than that of Holstein milk under high-altitude feeding, and the bacterial community may be affected by milk components.