The purpose of this study was to determine the circadian variation and differences of blood glucose and lipid metabolism， immunity， oxidation and antioxidation related indexes in postpartum healthy dairy cows and subclinical ketosis dairy cows， and to evaluate the effects of ketosis on the circadian physiological homeostasis of energy metabolism， immunity and oxidative stress in dairy cows from the perspective of the circadian clock. The blood samples of postpartum healthy group （postpartum 3-21 d， blood BHBA<1.2 mmol·L^-1， n=10） and subclinical ketosis group （postpartum 3-21 d， 1.2 mmol·L^-1<blood BHBA<3.0 mmol·L^-1， n=10） were collected at different time points （09：00， 17：00 and 01：00）. The blood ketone blood glucose meter and cholesterol determination kit were used to determine the diurnal changes of glucose and lipid metabolism indexes of dairy cows in each group. The white blood cells in the blood were isolated and total RNA was extracted. The circadian changes of inflammation-related genes and circadian clock genes in white blood cells were detected by real-time fluorescence quantitative PCR. The changes of blood oxidative stress indexes were detected by ELISA kit. The results showed that compared with the healthy group， the blood β-hydroxybutyrate （BHBA） content of dairy cows in the subclinical ketosis group was significantly increased （P<0.000 1）， the blood glucose concentration （P<0.01） and the plasma cholesterol content （P<0.000 1） were significantly decreased， and the blood glucose content （P<0.05） of dairy cows in the subclinical ketosis group exhibited significant difference between day and night. The changes of hydrogen peroxide （H₂O₂） （P<0.05）， catalase （CAT） （P<0.05）， superoxide dismutase （SOD） （P<0.05） and β-N-acetylglucosaminidase （NAG） （P<0.05） in plasma of healthy cows had significant diurnal differences. The changes of plasma H₂O₂ （P<0.05） and CAT （P<0.01） in subclinical ketosis group were significantly different between day and night. Compared with the healthy group， the contents of H₂O₂ （P<0.01） and malondialdehyde （MDA） （P<0.000 1）， and the activities of glutathione peroxidase （GSH-Px） （P<0.05） and NAG （P<0.000 1） in the plasma of dairy cows in the subclinical ketosis group were significantly increased. The qPCR results showed that the mRNA expression of circadian clock genes BMAL1 （P<0.01）， RORα （P<0.05） and PER2 （P<0.01） in white blood cells of healthy cows had significant day-night differences. The mRNA expression of circadian clock genes BMAL1 （P<0.05）， NR1D1 （P<0.05）， RORα （P<0.01） and PER2 （P<0.05） in white blood cells of subclinical ketosis cows had significant day-night differences. Compared with the healthy group， the circadian expression patterns of BMAL1 （P<0.05）， RORα （P<0.01） and PER2 （P<0.01） mRNA in blood leukocytes of subclinical ketosis cows were significantly changed. The mRNA expression of inflammatory cytokines interleukin-6 （IL-6） （P<0.000 1）， interleukin-8 （IL-8） （P<0.05）， interleukin-10 （IL-10） （P<0.05）， interleukin-1β （IL-1β） （P<0.01）， and chemokine ligand 5 （CCL5） （P<0.01） in the blood of healthy cows showed significant circadian differences. The mRNA expression of IL-6 （P<0.01）， IL-10 （P<0.01） and IL-1β （P<0.000 1） in blood leukocytes of dairy cows with subclinical ketosis showed significant difference between day and night. Compared with the healthy group， the circadian expression patterns of IL-6， IL-10 and IL-1β mRNA in the blood leukocytes of dairy cows in the subclinical ketosis group changed， and the circadian differences in the expression of IL-8 and CCL5 mRNA disappeared. In summary， there are circadian differences in some blood glucose and lipid metabolism indexes， oxidative stress indexes， blood leukocyte circadian clock genes and inflammatory factor gene expression between healthy cows and subclinical ketosis cows. However， the circadian changes of some blood glucose and lipid metabolism indexes， oxidative stress indexes， blood leukocyte circadian clock genes and inflammatory factor gene expression in subclinical ketosis cows are significantly changed. The steady-state of circadian changes of plasma oxidation and antioxidant system is abnormal， and the circadian changes of circadian clock genes and inflammatory related gene expression in blood leukocytes are abnormal. The decrease of body resistance associated with ketosis may be related to the abnormal circadian rhythm of inflammatory factor expression in peripheral blood leukocytes of dairy cows. The above research preliminarily analyzed the characteristic changes of blood indexes of ketosis cows from the perspective of circadian clock， which provided research basis and theoretical basis for the accurate prevention and control and accurate diagnosis of ketosis in dairy cows.