Objectives : The present study was carried out to investigate the effect of Hyperici Japonici Herba on the proliferation and activation of eosinophils which were prepared from lung cells of asthma-induced mice by ovalbumin(OVA) treatment. Methods : C57BL/6 mouse was exposed to OVA three times a week for 6 weeks. The mouse lung tissues were dissected out, chopped and dessiciated with collagenase(1${mu}g$/ml). Eosinophils were activated by rIL-3/rmIL-5 co-treatments. The lung cells were treated with extract of Hyperici Japonici Herba(EHH), incubated for 48 hr at $37^{circ}C$, and analyzed by flow cytometer. ELBA, RT-PCR, immunocytochemistry stain. Results : The cell number ratio of granulocyte, $CD3e^-$/$CCR3^+$, $CD3e^+$/$CD69^+$, $CD4^+$, $CD23^+$/$B220^+$ cells was increased in rmIL-5/rIL-3 treated control group compared to the normal group. Cells numbers in the experimental animal group treated with EHH was all decreased. In ELISA analysis, IL-4, IL-5, IL-13 protein levels and histamine release level were greatly increased in the control group compared to the normal animal group, then significantly decreased in the experimental group with 100 ${mu}g$/ml of EHH treatment. In RT-PCR analysis, the HT value of IL-4, IL-5, IL-13, CCR3, Eotaxin were increased in the control group compared to the normal animal group, then decreased in the experimental group with 100 ${mu}g$/ml of EHH treatment. And eosinophil proliferation levels were 18847${pm}$1527(cpm) in the control group, 4676${pm}$972(cpm) in the positive control group, and 8675${pm}$159(cpm), 11352${pm}$1005(cpm), 14325${pm}$677(cpm) in the experimental group with 100 ${mu}g$/ml, 10 ${mu}g$/ml, 1 ${mu}g$/ml of EHH treatment. Conclusions : The present data suggested that Hyperici Japonici Herba may have an effects on the inhibition of parameters associated with asthma responses in eosinpophils, and thus implicate the possibility for the clinical application of EHH.