Objective: To understand the hemoglobin, ferritin levels and physiological changes of normal pregnant women after vaginal delivery, and to discussing the timing and threshold screening for postpartum anemia. Methods: The study population included women who delivered vaginally after 37 weeks’ gestation (n=103). They were tested for hemoglobin, erythrocyte (RBC) and hematocrit (HCT) before the delivery and at 24 h, 48 h, 72 h, 7 d and 42 d after the delivery, tested for ferritin before the delivery and at 24 h, 7 d and 42 d after the delivery. According to the ferritin level before the delivery, it was divided into a normal group and an iron deficiency group (ferritin <20 μg/L was considered to be iron deficiency). We used two factors repeated measurement ANOVA, t-test, and single-factor repeated measurement ANOVA to analyze the data. Results: The interaction between group and time had no statistically significant effect on Hb and RBC (P>0.05). Both of them showed the same trend over time: a significant decrease in postpartum 3 d followed by a significant increase to postpartum 7 d, and a slow increase from postpartum 7 d to postpartum 42 d. Interaction between group and time factors had statistical significance on HCT and SF (P<0.05). The postpartum SF showed a continuous upward trend, which was significant from 24 h to 7 d after the delivery. The growth trend of iron deficiency group was slower than that of the normal group. There was no significant difference in the HCT levels between the two groups before deliver (P>0.05), and the HCT levels in the iron deficiency group at different postpartum time were lower than those in the normal group, and the difference was statistically significant (P<0.05). The Hb level reached its lowest point at 24 h after the delivery, and rose significantly close to the prenatal level at 7 d after the delivery, with no statistically significant difference (P>0.05). Conclusion: Due to blood dilution, hemoglobin decreased significantly within 3 d after the delivery, leading to physiological anemia. It is more accurate to screen hemoglobin at 7 d after the delivery. It is suggested that joint ferritin screening assess maternal iron deficiency.