Abstract: Objective: To explore the levels IL-12,IFN-γ,IL-10 and IL-4 in peripheral blood of normal pregnant women and preeclampsia patients and its clinical significance,and investigate the role of Th1/Th2 cytokines of helper T cell in pathogenesis of preeclampsia.Methods: Thirty pregnant women with preeclampsia and 30 normal pregnant women without complications were divided into the observation group and control group,respectively.The serum levels of IL-12,IFN-γ,IL-10 and IL-4 in two groups were detected and analyzed.Results: The serum protein levels and mRNA expressions of IL-12 and IFN-γ in observation group were higher than that in control group(P < 0.01).The serum protein levels and mRNA expressions of IL-4 and IL-10 in observation group were lower than control group(P < 0.01).Conclusions: The type Th1cytokine expression increasing,the Th2 expression decreasing and proportion imbalance of Th1/Th2 may be the important causes of preeclampsia.