The A549 cells were treated with different concentrations （0.025， 0.050， 0.100， 0.200 and 0.400 mmol·L^－1） of PMI for 24， 48 and 72 h，respectively. The proliferation activity of the A549 cells was detected by MTT method， and the half inhibitory concentration （IC₅₀） was calculated.The A549 cells were treated with different concentrations （0.050，0.100，0.200 mmol·L^－1）of PMI or 0.200 mmol·L^－1 PMI combined with p38 MAPK inhibitor SB203580 for 48 h. The cells were divided into blank control group， different concentrations（0.050， 0.100 and 0.200 mmol·L^－1） of PMI groups and combination group （0.200 mmol·L^－1 PMI + 20 μmol·L^－1 SB203580）.The apoptotic rates of the A549 cells in various groups were detected by Annexin Ⅴ-FITC/PI method； the expression levels of apoptosis-related proteins B-cell lymphoma-2 （Bcl-2），Bcl-2 associated X protein（Bax），and cleaved-caspase-3 and mitogen-activated protein kinases （p38MAPK）/p53 signaling pathway related proteins phosphorylaed p38MAPK （p-p38 MAPK） （Thr180/Thr182）， p-p53 （ser15）， p53， PUMA， and murine double minute 2（MDM2） in the A549 cells in various groups were detected by Western blotting method the localization of p53 protein of the A549 cells in various groups was observed by immunofluorescence assay.

Compared with control group， the survival rates of the A549 cells in 0.10 and 0.20 mmol·L^－1 PMI groups were decreased （P<0.05）， the apoptotic rates were increased （P<0.05）， and the expression levels of Bax， cleaved-caspase-3， p-p38 MAPK （Thr180/Thr182）， p-p53 （ser15）， p53 and PUMA proteins were increased （P<0.05），and the expression levels of Bcl-2 and MDM2 proteins were decreased （P<0.05）.Compared with 0.20 mmol·L^－1 PMI group， the survival rate of the A549 cells in combination group was increased （P<0.05）， the apoptotic rate was decreased （P<0.05）， the expression levels of Bax， cleaved-caspase-3， p-p38MAPK （Thr180/Thr182）， p-p53 （ser15）， p53， and PUMA proteins were decreased （P<0.05）， while the expression levels of Bcl-2 and MDM2 proteins were increased （P<0.05）.The immunofluorescence results showed that the phenomenon of p53 protein transferring from cytoplasm to nucleus could be seen， and the p53 protein was expressed in both the cytoplasm and nucleus.

Peiminine can induce the apoptosis of the A549 cells， and its molecular mechanism may be related to the p38 MAPK/ P53 signaling pathway mediated apoptosis.