Objective:To investigate the expression of miR-486 in serum of patients with gastric cancer and its value to auxiliary diagnosis. Methods: The serum of 100 patients with pathological confirmed GC, 30 gastric polyps and 50 healthy controls were recruited. Serum miR-486 expression was determined by fluorescent quantity PCR. Serum CEA, CA199 and CA724 were determined by chemiluminescence method. Comparison of differences of serum miR-486 between groups was performed by Mann-Whitney U test. Analysis the relationship between serum expression of miR-486 in gastric cancer patients and its clinical pathological characteristics was performed by χ2 test. The relationships between miR-486 and CEA, CA199, CA724 were examined by Spearman correlation analysis. ROC curve and AUC (95% CI) were used to evaluate their diagnosis efficiency. Results: The relative expression of miR-486 in GC, gastric polyps, healthy controls were 0.454 (0.225, 0.653), 0.121 (0.083, 0.166), 0.063 (0.013, 0.119),respectively. The relative expression of miR-486 in GC was significantly higher than that in gastric polyps and healthy controls (P < 0.001). The difference between gastric polyps and healthy controls is not significant (P > 0.05). The differences of expression of miR-486 in serum of GC in tumor differentiation (P=0.046), TNM(P=0.013) and the occurrence of lymph node metastases (P=0.006)were statistically significant except for age, gender, tumor area (P > 0.05). The relative expression of miR-486 in GC had a correlation with CEA (r=0.213, P=0.034),CA724 (r=0.297, P=0.003) but no obvious correlation with CA199 (r=0.037, P=0.714). AUC of serum miR-486 was 0.839, 0.774~0.904 (95%CI) in discriminating GC from healthy controls. Conclusion: The relative expression of miR-486 in GC was significantly higher than that in gastric polyps and healthy controls, serum miR-486 may be a biomarker for the auxiliary diagnosis of GC.