Abstract: In order to explore the relationship between the levels of blood hormones and postpartum retained placenta（RP） in each stage of the perinatal period of Holstein cows in Ningxia area, in the experiment, six cows with non-retained placenta（NRP group） and six cows with retained placenta（RP group） were selected; the tail vein blood on the（-21±2）th,（-14±2）th,（-7±2）th, 0 th, 7 th, 14 th, 21 th days of perinatal period was collected. The concentrations of endothelin（ET）,progesterone（P₄） and estradiol（E₂） in the blood were measured by radioimmunoassay, and the concentration of 6-ketoprostaglandin（6-K） in the blood was measured by ELSIA method. The results showed that on the（-21±2）th,（-14±2）th,（-7±2）th, 0 th, 7 th, 14 th, 21 th days of perinatal period, partial hormone indexes in the blood of dairy cows in the NRP group and the RP group would change accordingly over time. The blood ET concentration in the RP group was higher on the（-21±2）th,（-14±2）th,（-7±2）th, 0 th, 21 th days, and lower on the 7 th, 14 th days, than that in the NRP group, but the differences were not significant（P＞0.05）. The concentration of P₄ in the blood of dairy cows in the RP group was higher than that in the NRP group on the（-7±2）th, 0 days（P＞0.05）;the E₂ concentration in the blood of dairy cows in the RP group was significantly higher than that in the NRP group on the 0 th day（P＜0.05）;the concentration of 6-K in the blood of dairy cows in the RP group was significantly lower than that in the NRP group on the（-7±2）th day（P＜0.05）. The results suggested that the concentration change trend of P₄,E₂ and 6-K in the blood on the（-7±2）th and 0 th days during the perinatal period could be used to warn the occurrence of retained placenta for dairy cows.