Abstract: Objective To investigate the effects of gefitinib combined with bruceolic oil emulsion on the proliferation and apoptosis of human lung adenocarcinoma cell lines PC-9 and A549 and related mechanism. Methods PC-9 and A549 cell lines in logarithmic phase were divided into control group and experimental groups. MTT colorimetry, TUNEL assay and flow cytometry were used to detect the effects of gefitinib combined with bruceolic oil emulsion on cell proliferation, cell apoptosis and cell cycle in the experimental groups. Results Gefitinib and Bruceolic oil emulsion could inhibit the growth, proliferation and increase the apoptosis of PC-9 and A549 cell lines in a dose- and time-dependent manner. The growth inhibitory and apoptotic effects of the concomitant administration of gefitinib and bruceolic oil emulsion were higher than other groups. Conclusion Gefitinib and Bruceolic oil emulsion could significantly inhibit the proliferation and induce the apoptosis of PC-9 and A549 cell lines. The effects might be related to the retardation of drugs on cell cycle. Bruceolic oil emulsion has a synergy -increasing effect to gefitinib.