To observe the change of the proportion of Th1 cells to Th2 cells in postpartum depression (PPD) rats,and to explore the mechanism of Shenqi Jieyu Decoction (SJD) on regulating the balance of PPD Th1/Th2 from T cell immunity.Methods:A total of 90 female SD rats were divided into normal group,model group,sham-operated group,SJD group and medicine group with 6 rats in each group.The rats were administrated for 1,2,and 4 weeks.The proportion of Th1 cells to Th2 cells in peripheral blood of each group was observed with flow cytometry in 3 times,and the ratio of Th1/Th2 was calculated.Results:Proportion of Th1 cells to Th2 cells in model group was lower than that in normal group (P<0.01); and it increased in 2-week and 4-week time point than that in normal group (P<0.01); Proportion of Th1 to Th2 in model group was increased in 1-week time point than that in normal group (P<0.05),while it was lower in 2-week and 4-week time point (P<0.01); Th1 cells in SJD group were increased in 1-week time point compared with that in model group (P>0.05),while it decreased in 2-week and 4-week time point (P<0.01).The proportion of Th2 cells in SJD group increased in 1-week time point compared with the model group (P<0.05),while it decreased in 2-week and 4-week time point (P<0.01).Proportion of Th1 to Th2 was decreased in SJD group in 1-week time point compared with that in model group (P>0.05); It was increased in the 2-week time point (P<0.05),while it increased in 4-week time point (P<0.01).Conclusion:Imbalance in the ratio between Th1 and Th2 may be a potent pathogenesis of PPD,and therapeutic effect of SJD on PPD is worked by regulating Th1 cells and Th2 cells.