The concentration of serum calcium (Ca), phosphorus (P), alkaline phosphatase (AKP), parathyroid hormone (PTH) and calcitonin (CT) of 66 healthy pregnant women were measured at 2nd trimester, full term, 3 days and 6 weeks postpartum. These parameters were also measured in 56 patients with moderate or severe PIH in late pregnancy. The results showed that in spite of the obvious changes observed in these parameters at various periods, regulatory system of calcium metabolism in normal pregnancy was not affected. By contrast, calcium metabolism imbalance was seen in patients with moderate and severe PIH. The occurrence of PIH between two groups of pregnant women (50 each) with or without calcium supplement was compared. The pattern of calcium metabolism in normal pregnancy was summarized, and the pathogenesis of PIH related to calcium metabolism was discussed. The study provides an important basis for calcium supplementation during pregnancy and for using calcium antagonists to treat PIH patient.