Objective To investigate the effect of Terpinen-4-ol on the proliferation of lung adenocarcinoma A-549 cells and its related mechanism. Methods A-549 cells were treated with different concentrations of Terpinen-4-ol. The inhibitory effect of Terpinen-4-ol on A-549 cells was tested by MTT method. Cell grow ability was determined by CCK-8 colorimetry. The ultrastructure of A549 cells were observed by transmission electron microscopy before and after Terpinen-4-ol treatment. The changes of cell cycle, apoptosis, and the level of intracel-lular calcium were inspected by flow cytometry. Inoculated the lung adenocarcinoma A-549 cells on the nude mice to form transplantation tumor. The experimental nude mice with transplantation tumors were divided into three groups:negative control group,high dose positive con-trol group and low dose positive control group. The mice were given continuously intraperitoneal injection for 10 days, and then the transplan-tation tumors were taken and the size and weight of them were detected. Results After Terpinen-4-ol treatment for 24 h,MTT assay showed that the IC50 value of A549 cells was 0. 067% v/v. The growth curves of positive control groups were significantly smooth than the negative control group. The formation of autophagosome increased after treatment with Terpinen-4-ol. The results of flow cytometry showed that the cell cycle was arrested in S phase,Terpinen-4-ol could induce apoptosis of A549 cell, The intracellular calcium concentrations in positive control groups were significantly higher than the negative control group(P<0. 05). Low dose group and high dose group restrained the growth of the transplantation tumor obviously, and the tumor inhibitory rate were 53. 33% and 77. 76% respectively. Conclusion Terpinen-4-ol has inhibitory effect on the proliferation of A-549 cells in vitro and in vivo.