Abstract: In this study, 24 cows with similar age, birth and body condition were chosen and grouped by serum β-hydroxybutyric acid (BHBA) content. The cows with greater BHBA content (>1.2 mmol·L^-1) were assigned as the experiment group, and cows with less BHBA content (≤1.2 mmol·L^-1) were assigned as the control group. The concentration of biochemical indicators in the serum which taken at the 14th, 7th, 1st day of prenatal and the 1st, 7th, 14th, 21th, 28th day of postpartum, were tested and the changing trends of them during the experimental stage were analyzed. The results shown that the concentration of serum BHBA in the experiment group was very significantly higher than that in the control group (P<0.01); nonesterified fatty acid (NEFA) was significantly higher than that in the control group (P<0.05); glucose (GLU) was very significantly lower than that in the control group (P<0.01); blood urea nitrogen (BUN) was very significantly higher than that in the control group (P<0.01); Other indices were difference in different stages. In the two groups, the concentration of serum BHBA was in a high level at the 7th to the 21st day of postpartum, NEFA was highest at the 21st day of postpartum, the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were highest at the 7th day of postpartum. This test proved that subclinical ketosis can occur at the 7th day of postpartum, and occur easily at the 21st day of postpartum.