Gastric cancer is the second leading cause of cancer death in the world. There is evidence that shows genetic and epigenetic change in stomach cancer is as a result of a variety of oncogenes, tumor suppressor genes, genes that repair the DNA, genes regulating cell cycle and cell adhesion molecules. P16 is an Inhibitor of protein kinase that is dependent on Cyclin D. Inactivation of this gene as a tumor suppressor gene, cause to cancer. This study was conducted to Investigation the P16 hyper-metylation status in serum of gastric cancer patients in Ardabil province as the prognostic factor for early diagnosis of gastric cancer. 82 Blood samples of patients with gastric cancer was prepared from Aras clinic of Imam Khomeini hospital. After DNA extraction from serum, using methylation-specific PCR assay it was examined the existence of hypermethylation in the P16 gene promoter. Incidence of free DNA in the serum of patients was 59.8%. P16 gene promoter was hyper methylated in 20.4% of subjects. Data analysis showed a statistically significant association between P16 methylation status and types of the adenocarcinoma. But there was no statistically significant association between methylation status of P16 with other features (age, sex, tumor location). This study showed P16 gene methylation of occur in some of gastric cancer patients. This result suggests that p16 methylation may be a prognostic marker for early diagnosis of gastric cancer.