Abstract: Objective To explore the effect of Periplaneta americana extract on human lung cancer cell H125 and its mechanism.Methods The human lung cancer cells H125 were divided into negative control group,positive control group(cisplatin 10μg/mL),and Periplaneta americana extract group(10,20,40 μg/mL).Methyl thiazolyl tetrazolium(MTT) colorimetric method was adopted to observe the growth of H125 cells.Cell cycle,apoptosis and mitochondrial membrane potential were measured with flow cytometry.The expression of Bax and Bcl-2 protein were detected with Western blot.Results Periplaneta americana extract could inhibit the growth of human lung cancer cell H125,with a 50% inhihition concentration(IC₅₀) of 24.8 μg/ml.Periplaneta americana extract could significantly reduce the mitochondrial membrane potential in human lung cancer cell H125.Compared with the control group,the percentage of green fluorescence(34.12±0.21%) and apoptosis rate(24.76±0.168%) increased;the proportion of G2/M phase cells(23.12±0.159%) decreased and the proportion of S stage cells(20.92±0.096%) increased in the H125 cells treated with 40 μg/mL extract;the expressions of Bax and Bcl-2 protein were also inhibited.Conclusion Periplaneta americana extract can inhibit the growth of human lung cancer cell H125,arrest the cell cycle in S phase,and induce apoptosis through mitochondrial pathway.