Abstract: This study is to explore the mechanism and effect of N,N′-di-(M-methylphenyl)-3,6-dimethyl-1,4-dihydro-1,2,4,5-tetrazine-1,4-dicarboamide (ZGDHu-1) on proliferation and apoptosis of A549 cells in vitro and on A549 xenograft tumor in nude mice. With different concentrations of ZGDHu-1 at different times were used to treat A549 cells in vitro. The proliferation was determined by living cell count, SRB assay and Brdu-ELISA. Cell apoptosis was determined by cell morphology, DNA agarose gel electrophoresis, DNA content, Annexin V/PI and Hoechst 33258 labeling method. The nude mice model of A549 xenograft tumor was established by subcutaneous inoculation. The suppression activity of ZGDHu-1 by intraperitoneal injection on xenograft mice model was detected. The expressions of bcl-2, bax and p53 gene and protein were analyzed by RT-PCR and flow cytometry. ZGDHu-1 can inhibit A549 cell proliferation viability within a certain range of treating time and does, and a majority of A549 cells were arrested in G₂-M phase. The A549 cells apoptosis was confirmed by typical cell morphology, DNA fragment, Sub G₁ phase, Hoechst 33258 and Annexin V/PI labeling method with a time and dose related manner. When the xenograft tumor mice model were treated with 10, 20 and 40 mg·kg^-1 ZGDHu-1 for 14 days, the tumor growth inhibition rate were 43.7%, 56.9% and 60.0%, respectively. The expression of bax, bax/bcl-2 and p53 gene and protein increased significantly and bcl-2 decreased slightly by the treatment of ZGDHu-1. ZGDHu-1 can significantly suppress the growth of A549 xenograft tumor in vivo and inhibited proliferation by inducing tumor cell apoptosis in vitro. The mechanism may associate with its up-regulation of bax and p53 during the apoptosis process.