In this paper, immunohistochemistry and fluorescence in situ hybridization (FISH) were used to detect HER2 gene amplification and expression of PD-L1 and PD-1 in gastric cancer tissue and to explore the target and correlation of antitumor drug therapy for gastric cancer to provide help for the prognosis and targeted antitumor drug therapy of gastric cancer. This evidence concerns the gene ERBB2 and gastric cancer.