OBJECTIVE： To study the inhibitory mechanism of timosaponin B-Ⅱ （TB-Ⅱ） on the proliferation and migration of human lung cancer A549 cells. METHODS： A549 cells were treated with TB-Ⅱ [0 （blank control）， 1， 10 and 100 μg/ml] for 48 h， and total RNA and total protein were extracted respectively. Real time fluorescence quantitative-PCR and Western blot were used to detect mRNA and protein levels of IL-18. IL-18 in A549 cells was silenced by transfection； the expression of IL-18 mRNA and protein were compared among untransfection group， negative control group and transfection group； and then human lung cancer A549 cells with silenced gene were treated with 10 μg/ml TB-Ⅱ for 24， 48 and 72 h. The activity of cell proliferation was detected with CCK-8， and the change of cell migration ability was observed by streak method. RESULTS： Compared with blank control， the expression of IL-18 mRNA and protein in A549 cells all increased after treated with TB-Ⅱ（P＜0.05 or P＜0.01）， and were positively correlated with concentration. Compared with untransfection group， the expression of IL-18 mRNA and protein decreased in transfection group （P＜0.01）. Compared with untransfected cell treated with TB-Ⅱ， the viability and migration ability of A549 cells with transfection gene increased after treated with TB-Ⅱ for 72 h （P＜0.01）. CONCLUSIONS： TB-Ⅱ can inhibit the proliferation and migration of A549 cells by up-regulating IL-18 gene expression.