Gastric cancer is a major global health challenge, associated with high mortality and limited therapeutic options. Ginsenoside Rg3 (Rg3), a bioactive compound derived from ginseng, has been shown to possess significant anticancer properties, particularly through immune modulation. In this study, we explored the therapeutic potential of Ginsenoside Rg3 hydrogel in the treatment of gastric cancer, focusing on its ability to target fibroblast activation protein (FAP), a key mediator of tumor progression. Using reverse molecular docking and gene expression analysis, we identified FAP as a primary molecular target of Rg3. Preclinical evaluations revealed that Rg3 hydrogel effectively inhibited the proliferation and invasion of gastric cancer cells in vitro. Furthermore, the hydrogel promoted immunogenic cell death, resulting in a robust immune response against the tumor. Our findings suggest that Ginsenoside Rg3 hydrogel holds promise as a novel immune-based therapeutic strategy for gastric cancer, offering a potential pathway to improved clinical outcomes and treatment strategies.