Objective: siRNA-ZNF 139 was applied to silence ZNF 139gene expression of orthotopic implantation tumor of human gastric cancer cell line SGC-7901 in nude mice.The purpose of this study is to investigate the effect of siRNA-ZNF139 on cell apoptosis of orthotopic implantation tumor of human gastric cancer in nude mice, as well as the mechanism of its effect.Methods: The recombinant plasmid was extracted from the endotoxin-free kit.After extraction, the concentration and purity of the extracted recombinant plasmid were examined using ultraviolet spectrophotometry.The concentration and purity of the extracted plasmid examined by ultraviolet spectrophotometry met the requirements of the follow-up experiment.The orthotopic implantation model of human gastric cancer in nude mouse was built.Tumor growth and tumor weight were measured.The gastric cancer cell activity in the three groups was determined by MTT assay.The apoptosis rate of gastric cancer cells in nude mice in the three groups was detected by flow cytometry.ZNF139, Bax, and Bcl-2 mRNA expressions of gastric cancer cell in nude mice were determined and compared through RT-PCR.