Objective: To study the significance of Leptin and the activity of erythrocyte membrane Ca2+-ATPase(EMCA) in the development of hypertensive disorder complicating pregnancy. Methods: Radioimmunoassay was used to test the level of serum Leptin,and the activity of EMCA was determined chemically in 38 pregnant women with hypertensive disorder complicating pregnancy and 36 normotensive pregnant women. Results: The level of serum Leptin in hypertensive disorder complicating pregnancy(gestational hypertension: 13.76 ± 3.46 ng/ml; preeclampsia:15.76 ± 5.47 ng/ml; eclampsia: 18.32 ± 6.38 ng/ml)was significantly higher than that in normotensive pregnant women(11.33 ± 2.93 ng/ml),respectively. The average EMCA activity of patients with hypertensive disorder complicating pregnancy(gestational hypertension:1.65 ± 0.24 μmol·pi/mg·h ; preeclampsia:1.37 ± 0.19 μ mol·pi/mg·h; eclampsia:1.12 ± 0.14 μ mol·pi/mg·h) was significantly lower than that of normotensive pregnant women(1.83 ± 0.38 μ mol·pi/mg·h),respectively. There was a negative correlation between the level of serum Leptin and the activity of RMCA in hypertensive disorder complicating pregnancy(r = -0.63). Conclusion: Inhibition of EMCA activity of erythrocyte in hypertensive disorder complicating pregnancy may increase cytoplasmic free calcium, which contributes to the development of hypertensive disorder complicating pregnancy. The negative correlation between the level of serum Leptin and the activity of EMCA, also suggested that serum Leptin and the activity of EMCA may play a role in the development of hypertensive disorder complicating pregnancy.