Gastric cancer is one of the most common malignant tumors in the world. In China, its morbidity and mortality are second only to lung cancer. Chemotherapy combined with targeted therapy brings survival benefits to patients with advanced gastric cancer. Targets for targeted therapy of gastric cancer include human epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), vascular endothelial growth factor (VEGF), mammalian target of rapamycin (mTOR) and Claudin 18.2 (CLDN 18.2). The main challenge of tumor molecule-targeted drugs is resistance. The main mechanisms of drug resistance include tumor establishment of compensatory signaling pathways, target protein changes, tumor microenvironment changes, tumor heterogeneity and tumor adaptation to targeted drugs. The combined action of multiple drug resistance mechanisms promotes the development of targeted drug resistance. In order to attract the attention of researchers, this paper reviews the mechanisms of drug resistance in gastric cancer-targeted therapy. In addition, the research status of drug resistance in molecule-targeted therapy of gastric cancer is summarized. It is of great clinical significance to explore the drug resistance mechanisms of targeted drugs and reverse drug resistance in gastric cancer. Last, the future development of molecule-targeted therapy is prospected.