Objective To investigate the expression of LncRNA RMST in gastric cancer and its value in diagnosis and prognosis. Methods Tumor and adjacent normal tissues were collected and analyzed from 92 gastric cancer patients. The expression of LncRNA RMST in these tissues was measured using RT-qPCR. ROC curve analysis was performed to evaluate the diagnostic value of LncRNA RMST for gastric cancer. Survival curves were plotted to assess the prognostic significance of LncRNA RMST in gastric cancer. Results LncRNA RMST expression was significantly lower in gastric cancer tissues than in normal tissues. Further analysis revealed that LncRNA RMST expression levels decreased progressively with advancing cancer stages and were significantly correlated with tumor size， TNM staging， and lymph node metastasis （P < 0.05）， with no significant correlation with patient age or gender. Additionally， ROC curve analysis indicated that LncRNA RMST has substantial diagnostic value in gastric cancer， with AUC of 0.76 （95% CI： 0.69 ~ 0.83， P < 0.01）， sensitivity of 70.31%， and specificity of 71.56%. Survival analysis showed that patients with high LncRNA RMST expression had significantly higher overall survival rates than those with low expression. Conclusion LncRNA RMST plays a critical role in the occurrence， progression， and prognosis of gastric cancer. It may serve as a potential biomarker for the diagnosis and prognosis of gastric cancer， offering new insights for clinical screening and therapeutic strategies.