Abstract: Objective: To analyze the characteristics of early and late onset severe preeclampsia (S-PE) involving organ damage and its relations with neonatal prognosis.Methods: Eighty mothers with severe preeclampsia and their 80 neonates were divived to two groups according to the onset time of severe preeclampsia:onset ≤ 34 weeks group and >34 weeks group.The clinical data, pattern of organ damage, complications, and maternal and neonatal outcomes were analyzed.Results: Placenta was the main organ damaged in the early onset group, and the occurrence rate was higher than that in the late onset group (P<0.005).Perinatal mortality was much higher in patients with organ damage than in those without organ damage.The early onset group had a poorer outcome than the late onset group.Conclusions: The earlier the onset of S-PE occurred, the severer the pathogenetic condtion is, and poorer the perinatal outcomes will be.Proper treatment and monitoring is essential for mothers with S-PE and the foetus.Pregnancy should be terminated in some of the cases if nessessary.